- 一个 Python 的数据分析库
- 关于 Pandas
- 获取 Pandas
- v0.25.0 版本特性(2019年7月18日)
- 安装
- 快速入门
- Pandas 用户指南目录
- IO工具(文本,CSV,HDF5,…)
- 索引和数据选择器
- 多层级索引和高级索引
- Merge, join, and concatenate
- Reshaping and pivot tables
- Pandas 处理文本字符串
- Working with missing data
- Categorical data
- Nullable 整型数据类型
- Visualization
- Computational tools
- Group By: split-apply-combine
- 时间序列与日期用法
- 时间差
- Styling
- Options and settings
- Enhancing performance
- Sparse data structures
- Frequently Asked Questions (FAQ)
- 烹饪指南
- Pandas 生态圈
- API 参考手册
- 开发者文档
- 发布日志
Visualization
We use the standard convention for referencing the matplotlib API:
In [1]: import matplotlib.pyplot as plt
In [2]: plt.close('all')
We provide the basics in pandas to easily create decent looking plots. See the ecosystemopen in new window section for visualization libraries that go beyond the basics documented here.
Note
All calls to np.random
are seeded with 123456.
Basic plotting: plot
We will demonstrate the basics, see the cookbook for some advanced strategies.
The plot
method on Series and DataFrame is just a simple wrapper around plt.plot()
open in new window:
In [3]: ts = pd.Series(np.random.randn(1000),
...: index=pd.date_range('1/1/2000', periods=1000))
...:
In [4]: ts = ts.cumsum()
In [5]: ts.plot()
Out[5]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d8c0ac50>
If the index consists of dates, it calls gcf().autofmt_xdate()
open in new window to try to format the x-axis nicely as per above.
On DataFrame, plot()
open in new window is a convenience to plot all of the columns with labels:
In [6]: df = pd.DataFrame(np.random.randn(1000, 4),
...: index=ts.index, columns=list('ABCD'))
...:
In [7]: df = df.cumsum()
In [8]: plt.figure();
In [9]: df.plot();
You can plot one column versus another using the x and y keywords in plot()
open in new window:
In [10]: df3 = pd.DataFrame(np.random.randn(1000, 2), columns=['B', 'C']).cumsum()
In [11]: df3['A'] = pd.Series(list(range(len(df))))
In [12]: df3.plot(x='A', y='B')
Out[12]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d97c1668>
Note
For more formatting and styling options, see formatting below.
Other plots
Plotting methods allow for a handful of plot styles other than the default line plot. These methods can be provided as the kind
keyword argument to plot()
open in new window, and include:
- ‘bar’ or ‘barh’ for bar plots
- ‘hist’ for histogram
- ‘box’ for boxplot
- ‘kde’ or ‘density’ for density plots
- ‘area’ for area plots
- ‘scatter’ for scatter plots
- ‘hexbin’ for hexagonal bin plots
- ‘pie’ for pie plots
For example, a bar plot can be created the following way:
In [13]: plt.figure();
In [14]: df.iloc[5].plot(kind='bar');
You can also create these other plots using the methods DataFrame.plot.
instead of providing the kind
keyword argument. This makes it easier to discover plot methods and the specific arguments they use:
In [15]: df = pd.DataFrame()
In [16]: df.plot.<TAB> # noqa: E225, E999
df.plot.area df.plot.barh df.plot.density df.plot.hist df.plot.line df.plot.scatter
df.plot.bar df.plot.box df.plot.hexbin df.plot.kde df.plot.pie
In addition to these kind
s, there are the DataFrame.hist(), and DataFrame.boxplot() methods, which use a separate interface.
Finally, there are several plotting functions in pandas.plotting
that take a Series
open in new window or DataFrame
open in new window as an argument. These include:
Plots may also be adorned with errorbars or tables.
Bar plots
For labeled, non-time series data, you may wish to produce a bar plot:
In [17]: plt.figure();
In [18]: df.iloc[5].plot.bar()
Out[18]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da446a90>
In [19]: plt.axhline(0, color='k');
Calling a DataFrame’s plot.bar()
open in new window method produces a multiple bar plot:
In [20]: df2 = pd.DataFrame(np.random.rand(10, 4), columns=['a', 'b', 'c', 'd'])
In [21]: df2.plot.bar();
To produce a stacked bar plot, pass stacked=True
:
In [22]: df2.plot.bar(stacked=True);
To get horizontal bar plots, use the barh
method:
In [23]: df2.plot.barh(stacked=True);
Histograms
Histograms can be drawn by using the DataFrame.plot.hist()
open in new window and Series.plot.hist()
open in new window methods.
In [24]: df4 = pd.DataFrame({'a': np.random.randn(1000) + 1, 'b': np.random.randn(1000),
....: 'c': np.random.randn(1000) - 1}, columns=['a', 'b', 'c'])
....:
In [25]: plt.figure();
In [26]: df4.plot.hist(alpha=0.5)
Out[26]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da345e48>
A histogram can be stacked using stacked=True
. Bin size can be changed using the bins
keyword.
In [27]: plt.figure();
In [28]: df4.plot.hist(stacked=True, bins=20)
Out[28]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da30b9b0>
You can pass other keywords supported by matplotlib hist
. For example, horizontal and cumulative histograms can be drawn by orientation='horizontal'
and cumulative=True
.
In [29]: plt.figure();
In [30]: df4['a'].plot.hist(orientation='horizontal', cumulative=True)
Out[30]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da69fd68>
See the hist
open in new window method and the matplotlib hist documentationopen in new window for more.
The existing interface DataFrame.hist
to plot histogram still can be used.
In [31]: plt.figure();
In [32]: df['A'].diff().hist()
Out[32]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65dac9d240>
DataFrame.hist()
open in new window plots the histograms of the columns on multiple subplots:
In [33]: plt.figure()
Out[33]: <Figure size 640x480 with 0 Axes>
In [34]: df.diff().hist(color='k', alpha=0.5, bins=50)
Out[34]:
array([[<matplotlib.axes._subplots.AxesSubplot object at 0x7f6601550cc0>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f66079a9400>],
[<matplotlib.axes._subplots.AxesSubplot object at 0x7f65f87ac828>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f6604bd6b70>]],
dtype=object)
The by
keyword can be specified to plot grouped histograms:
In [35]: data = pd.Series(np.random.randn(1000))
In [36]: data.hist(by=np.random.randint(0, 4, 1000), figsize=(6, 4))
Out[36]:
array([[<matplotlib.axes._subplots.AxesSubplot object at 0x7f6601550ef0>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d9b82438>],
[<matplotlib.axes._subplots.AxesSubplot object at 0x7f65dc30ba58>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65f63c2320>]],
dtype=object)
Box plots
Boxplot can be drawn calling Series.plot.box()
open in new window and DataFrame.plot.box()
open in new window, or DataFrame.boxplot()
open in new window to visualize the distribution of values within each column.
For instance, here is a boxplot representing five trials of 10 observations of a uniform random variable on [0,1).
In [37]: df = pd.DataFrame(np.random.rand(10, 5), columns=['A', 'B', 'C', 'D', 'E'])
In [38]: df.plot.box()
Out[38]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da17f898>
Boxplot can be colorized by passing color
keyword. You can pass a dict
whose keys are boxes
, whiskers
, medians
and caps
. If some keys are missing in the dict
, default colors are used for the corresponding artists. Also, boxplot has sym
keyword to specify fliers style.
When you pass other type of arguments via color
keyword, it will be directly passed to matplotlib for all the boxes
, whiskers
, medians
and caps
colorization.
The colors are applied to every boxes to be drawn. If you want more complicated colorization, you can get each drawn artists by passing return_type.
In [39]: color = {'boxes': 'DarkGreen', 'whiskers': 'DarkOrange',
....: 'medians': 'DarkBlue', 'caps': 'Gray'}
....:
In [40]: df.plot.box(color=color, sym='r+')
Out[40]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da880b00>
Also, you can pass other keywords supported by matplotlib boxplot
. For example, horizontal and custom-positioned boxplot can be drawn by vert=False
and positions
keywords.
In [41]: df.plot.box(vert=False, positions=[1, 4, 5, 6, 8])
Out[41]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65db18ffd0>
See the boxplot
open in new window method and the matplotlib boxplot documentationopen in new window for more.
The existing interface DataFrame.boxplot
to plot boxplot still can be used.
In [42]: df = pd.DataFrame(np.random.rand(10, 5))
In [43]: plt.figure();
In [44]: bp = df.boxplot()
You can create a stratified boxplot using the by
keyword argument to create groupings. For instance,
In [45]: df = pd.DataFrame(np.random.rand(10, 2), columns=['Col1', 'Col2'])
In [46]: df['X'] = pd.Series(['A', 'A', 'A', 'A', 'A', 'B', 'B', 'B', 'B', 'B'])
In [47]: plt.figure();
In [48]: bp = df.boxplot(by='X')
You can also pass a subset of columns to plot, as well as group by multiple columns:
In [49]: df = pd.DataFrame(np.random.rand(10, 3), columns=['Col1', 'Col2', 'Col3'])
In [50]: df['X'] = pd.Series(['A', 'A', 'A', 'A', 'A', 'B', 'B', 'B', 'B', 'B'])
In [51]: df['Y'] = pd.Series(['A', 'B', 'A', 'B', 'A', 'B', 'A', 'B', 'A', 'B'])
In [52]: plt.figure();
In [53]: bp = df.boxplot(column=['Col1', 'Col2'], by=['X', 'Y'])
Warning
The default changed from 'dict'
to 'axes'
in version 0.19.0.
In boxplot
, the return type can be controlled by the return_type
, keyword. The valid choices are {"axes", "dict", "both", None}
. Faceting, created by DataFrame.boxplot
with the by
keyword, will affect the output type as well:
return_type= | Faceted | Output type |
---|---|---|
None | No | axes |
None | Yes | 2-D ndarray of axes |
'axes' | No | axes |
'axes' | Yes | Series of axes |
'dict' | No | dict of artists |
'dict' | Yes | Series of dicts of artists |
'both' | No | namedtuple |
'both' | Yes | Series of namedtuples |
Groupby.boxplot
always returns a Series
of return_type
.
In [54]: np.random.seed(1234)
In [55]: df_box = pd.DataFrame(np.random.randn(50, 2))
In [56]: df_box['g'] = np.random.choice(['A', 'B'], size=50)
In [57]: df_box.loc[df_box['g'] == 'B', 1] += 3
In [58]: bp = df_box.boxplot(by='g')
The subplots above are split by the numeric columns first, then the value of the g
column. Below the subplots are first split by the value of g
, then by the numeric columns.
In [59]: bp = df_box.groupby('g').boxplot()
Area plot
You can create area plots with Series.plot.area()
open in new window and DataFrame.plot.area()
open in new window. Area plots are stacked by default. To produce stacked area plot, each column must be either all positive or all negative values.
When input data contains NaN, it will be automatically filled by 0. If you want to drop or fill by different values, use dataframe.dropna()
or dataframe.fillna()
before calling plot.
In [60]: df = pd.DataFrame(np.random.rand(10, 4), columns=['a', 'b', 'c', 'd'])
In [61]: df.plot.area();
To produce an unstacked plot, pass stacked=False
. Alpha value is set to 0.5 unless otherwise specified:
In [62]: df.plot.area(stacked=False);
Scatter plot
Scatter plot can be drawn by using the DataFrame.plot.scatter()
open in new window method. Scatter plot requires numeric columns for the x and y axes. These can be specified by the x
and y
keywords.
In [63]: df = pd.DataFrame(np.random.rand(50, 4), columns=['a', 'b', 'c', 'd'])
In [64]: df.plot.scatter(x='a', y='b');
To plot multiple column groups in a single axes, repeat plot
method specifying target ax
. It is recommended to specify color
and label
keywords to distinguish each groups.
In [65]: ax = df.plot.scatter(x='a', y='b', color='DarkBlue', label='Group 1');
In [66]: df.plot.scatter(x='c', y='d', color='DarkGreen', label='Group 2', ax=ax);
The keyword c
may be given as the name of a column to provide colors for each point:
In [67]: df.plot.scatter(x='a', y='b', c='c', s=50);
You can pass other keywords supported by matplotlib scatter
open in new window. The example below shows a bubble chart using a column of the DataFrame
as the bubble size.
In [68]: df.plot.scatter(x='a', y='b', s=df['c'] * 200);
See the scatter
open in new window method and the matplotlib scatter documentationopen in new window for more.
Hexagonal bin plot
You can create hexagonal bin plots with DataFrame.plot.hexbin()
open in new window. Hexbin plots can be a useful alternative to scatter plots if your data are too dense to plot each point individually.
In [69]: df = pd.DataFrame(np.random.randn(1000, 2), columns=['a', 'b'])
In [70]: df['b'] = df['b'] + np.arange(1000)
In [71]: df.plot.hexbin(x='a', y='b', gridsize=25)
Out[71]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d96e4fd0>
A useful keyword argument is gridsize
; it controls the number of hexagons in the x-direction, and defaults to 100. A larger gridsize
means more, smaller bins.
By default, a histogram of the counts around each (x, y)
point is computed. You can specify alternative aggregations by passing values to the C
and reduce_C_function
arguments. C
specifies the value at each (x, y)
point and reduce_C_function
is a function of one argument that reduces all the values in a bin to a single number (e.g. mean
, max
, sum
, std
). In this example the positions are given by columns a
and b
, while the value is given by column z
. The bins are aggregated with NumPy’s max
function.
In [72]: df = pd.DataFrame(np.random.randn(1000, 2), columns=['a', 'b'])
In [73]: df['b'] = df['b'] = df['b'] + np.arange(1000)
In [74]: df['z'] = np.random.uniform(0, 3, 1000)
In [75]: df.plot.hexbin(x='a', y='b', C='z', reduce_C_function=np.max, gridsize=25)
Out[75]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d98ea390>
See the hexbin
open in new window method and the matplotlib hexbin documentationopen in new window for more.
Pie plot
You can create a pie plot with DataFrame.plot.pie()
open in new window or Series.plot.pie()
open in new window. If your data includes any NaN
, they will be automatically filled with 0. A ValueError
will be raised if there are any negative values in your data.
In [76]: series = pd.Series(3 * np.random.rand(4),
....: index=['a', 'b', 'c', 'd'], name='series')
....:
In [77]: series.plot.pie(figsize=(6, 6))
Out[77]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da5ff278>
For pie plots it’s best to use square figures, i.e. a figure aspect ratio 1. You can create the figure with equal width and height, or force the aspect ratio to be equal after plotting by calling ax.set_aspect('equal')
on the returned axes
object.
Note that pie plot with DataFrame
open in new window requires that you either specify a target column by the y
argument or subplots=True
. When y
is specified, pie plot of selected column will be drawn. If subplots=True
is specified, pie plots for each column are drawn as subplots. A legend will be drawn in each pie plots by default; specify legend=False
to hide it.
In [78]: df = pd.DataFrame(3 * np.random.rand(4, 2),
....: index=['a', 'b', 'c', 'd'], columns=['x', 'y'])
....:
In [79]: df.plot.pie(subplots=True, figsize=(8, 4))
Out[79]:
array([<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d915b0b8>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d9493a90>],
dtype=object)
You can use the labels
and colors
keywords to specify the labels and colors of each wedge.
Warning
Most pandas plots use the label
and color
arguments (note the lack of “s” on those). To be consistent with matplotlib.pyplot.pie()
open in new window you must use labels
and colors
.
If you want to hide wedge labels, specify labels=None
. If fontsize
is specified, the value will be applied to wedge labels. Also, other keywords supported by matplotlib.pyplot.pie()
open in new window can be used.
In [80]: series.plot.pie(labels=['AA', 'BB', 'CC', 'DD'], colors=['r', 'g', 'b', 'c'],
....: autopct='%.2f', fontsize=20, figsize=(6, 6))
....:
Out[80]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da0be4a8>
If you pass values whose sum total is less than 1.0, matplotlib draws a semicircle.
In [81]: series = pd.Series([0.1] * 4, index=['a', 'b', 'c', 'd'], name='series2')
In [82]: series.plot.pie(figsize=(6, 6))
Out[82]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d92543c8>
See the matplotlib pie documentationopen in new window for more.
Plotting with missing data
Pandas tries to be pragmatic about plotting DataFrames
or Series
that contain missing data. Missing values are dropped, left out, or filled depending on the plot type.
Plot Type | NaN Handling |
---|---|
Line | Leave gaps at NaNs |
Line (stacked) | Fill 0’s |
Bar | Fill 0’s |
Scatter | Drop NaNs |
Histogram | Drop NaNs (column-wise) |
Box | Drop NaNs (column-wise) |
Area | Fill 0’s |
KDE | Drop NaNs (column-wise) |
Hexbin | Drop NaNs |
Pie | Fill 0’s |
If any of these defaults are not what you want, or if you want to be explicit about how missing values are handled, consider using fillna()
open in new window or dropna()
open in new window before plotting.
Plotting Tools
These functions can be imported from pandas.plotting
and take a Series
open in new window or DataFrame
open in new window as an argument.
Scatter matrix plot
You can create a scatter plot matrix using the scatter_matrix
method in pandas.plotting
:
In [83]: from pandas.plotting import scatter_matrix
In [84]: df = pd.DataFrame(np.random.randn(1000, 4), columns=['a', 'b', 'c', 'd'])
In [85]: scatter_matrix(df, alpha=0.2, figsize=(6, 6), diagonal='kde')
Out[85]:
array([[<matplotlib.axes._subplots.AxesSubplot object at 0x7f65dc209da0>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d9df9588>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d8fb4b38>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d9834128>],
[<matplotlib.axes._subplots.AxesSubplot object at 0x7f65db04d6d8>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d8cdcc88>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d94e8278>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d9a67860>],
[<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d9a67898>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65da9f43c8>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65dacb7978>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65daddaf28>],
[<matplotlib.axes._subplots.AxesSubplot object at 0x7f65dbe47518>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d9016ac8>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d99540b8>,
<matplotlib.axes._subplots.AxesSubplot object at 0x7f65d9f84668>]],
dtype=object)
Density plot
You can create density plots using the Series.plot.kde()
open in new window and DataFrame.plot.kde()
open in new window methods.
In [86]: ser = pd.Series(np.random.randn(1000))
In [87]: ser.plot.kde()
Out[87]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d909c828>
Andrews curves
Andrews curves allow one to plot multivariate data as a large number of curves that are created using the attributes of samples as coefficients for Fourier series, see the Wikipedia entryopen in new window for more information. By coloring these curves differently for each class it is possible to visualize data clustering. Curves belonging to samples of the same class will usually be closer together and form larger structures.
Note: The “Iris” dataset is available hereopen in new window.
In [88]: from pandas.plotting import andrews_curves
In [89]: data = pd.read_csv('data/iris.data')
In [90]: plt.figure()
Out[90]: <Figure size 640x480 with 0 Axes>
In [91]: andrews_curves(data, 'Name')
Out[91]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da6e5518>
Parallel coordinates
Parallel coordinates is a plotting technique for plotting multivariate data, see the Wikipedia entryopen in new window for an introduction. Parallel coordinates allows one to see clusters in data and to estimate other statistics visually. Using parallel coordinates points are represented as connected line segments. Each vertical line represents one attribute. One set of connected line segments represents one data point. Points that tend to cluster will appear closer together.
In [92]: from pandas.plotting import parallel_coordinates
In [93]: data = pd.read_csv('data/iris.data')
In [94]: plt.figure()
Out[94]: <Figure size 640x480 with 0 Axes>
In [95]: parallel_coordinates(data, 'Name')
Out[95]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d96fbc88>
Lag plot
Lag plots are used to check if a data set or time series is random. Random data should not exhibit any structure in the lag plot. Non-random structure implies that the underlying data are not random. The lag
argument may be passed, and when lag=1
the plot is essentially data[:-1]
vs. data[1:]
.
In [96]: from pandas.plotting import lag_plot
In [97]: plt.figure()
Out[97]: <Figure size 640x480 with 0 Axes>
In [98]: spacing = np.linspace(-99 * np.pi, 99 * np.pi, num=1000)
In [99]: data = pd.Series(0.1 * np.random.rand(1000) + 0.9 * np.sin(spacing))
In [100]: lag_plot(data)
Out[100]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65da8b5e10>
Autocorrelation plot
Autocorrelation plots are often used for checking randomness in time series. This is done by computing autocorrelations for data values at varying time lags. If time series is random, such autocorrelations should be near zero for any and all time-lag separations. If time series is non-random then one or more of the autocorrelations will be significantly non-zero. The horizontal lines displayed in the plot correspond to 95% and 99% confidence bands. The dashed line is 99% confidence band. See the Wikipedia entryopen in new window for more about autocorrelation plots.
In [101]: from pandas.plotting import autocorrelation_plot
In [102]: plt.figure()
Out[102]: <Figure size 640x480 with 0 Axes>
In [103]: spacing = np.linspace(-9 * np.pi, 9 * np.pi, num=1000)
In [104]: data = pd.Series(0.7 * np.random.rand(1000) + 0.3 * np.sin(spacing))
In [105]: autocorrelation_plot(data)
Out[105]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d19556d8>
Bootstrap plot
Bootstrap plots are used to visually assess the uncertainty of a statistic, such as mean, median, midrange, etc. A random subset of a specified size is selected from a data set, the statistic in question is computed for this subset and the process is repeated a specified number of times. Resulting plots and histograms are what constitutes the bootstrap plot.
In [106]: from pandas.plotting import bootstrap_plot
In [107]: data = pd.Series(np.random.rand(1000))
In [108]: bootstrap_plot(data, size=50, samples=500, color='grey')
Out[108]: <Figure size 640x480 with 6 Axes>
RadViz
RadViz is a way of visualizing multi-variate data. It is based on a simple spring tension minimization algorithm. Basically you set up a bunch of points in a plane. In our case they are equally spaced on a unit circle. Each point represents a single attribute. You then pretend that each sample in the data set is attached to each of these points by a spring, the stiffness of which is proportional to the numerical value of that attribute (they are normalized to unit interval). The point in the plane, where our sample settles to (where the forces acting on our sample are at an equilibrium) is where a dot representing our sample will be drawn. Depending on which class that sample belongs it will be colored differently. See the R package Radvizopen in new window for more information.
Note: The “Iris” dataset is available hereopen in new window.
In [109]: from pandas.plotting import radviz
In [110]: data = pd.read_csv('data/iris.data')
In [111]: plt.figure()
Out[111]: <Figure size 640x480 with 0 Axes>
In [112]: radviz(data, 'Name')
Out[112]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65f66bd630>
Plot Formatting
Setting the plot style
From version 1.5 and up, matplotlib offers a range of pre-configured plotting styles. Setting the style can be used to easily give plots the general look that you want. Setting the style is as easy as calling matplotlib.style.use(my_plot_style)
before creating your plot. For example you could write matplotlib.style.use('ggplot')
for ggplot-style plots.
You can see the various available style names at matplotlib.style.available
and it’s very easy to try them out.
General plot style arguments
Most plotting methods have a set of keyword arguments that control the layout and formatting of the returned plot:
In [113]: plt.figure();
In [114]: ts.plot(style='k--', label='Series');
For each kind of plot (e.g. line, bar, scatter) any additional arguments keywords are passed along to the corresponding matplotlib function (ax.plot()
open in new window, ax.bar()
open in new window, ax.scatter()
open in new window). These can be used to control additional styling, beyond what pandas provides.
Controlling the legend
You may set the legend
argument to False
to hide the legend, which is shown by default.
In [115]: df = pd.DataFrame(np.random.randn(1000, 4),
.....: index=ts.index, columns=list('ABCD'))
.....:
In [116]: df = df.cumsum()
In [117]: df.plot(legend=False)
Out[117]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65dbdbc0f0>
Scales
You may pass logy
to get a log-scale Y axis.
In [118]: ts = pd.Series(np.random.randn(1000),
.....: index=pd.date_range('1/1/2000', periods=1000))
.....:
In [119]: ts = np.exp(ts.cumsum())
In [120]: ts.plot(logy=True)
Out[120]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65dbefdf98>
See also the logx
and loglog
keyword arguments.
Plotting on a secondary y-axis
To plot data on a secondary y-axis, use the secondary_y
keyword:
In [121]: df.A.plot()
Out[121]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65f8ef6b00>
In [122]: df.B.plot(secondary_y=True, style='g')
Out[122]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65f6297780>
To plot some columns in a DataFrame
, give the column names to the secondary_y
keyword:
In [123]: plt.figure()
Out[123]: <Figure size 640x480 with 0 Axes>
In [124]: ax = df.plot(secondary_y=['A', 'B'])
In [125]: ax.set_ylabel('CD scale')
Out[125]: Text(0, 0.5, 'CD scale')
In [126]: ax.right_ax.set_ylabel('AB scale')
Out[126]: Text(0, 0.5, 'AB scale')
Note that the columns plotted on the secondary y-axis is automatically marked with “(right)” in the legend. To turn off the automatic marking, use the mark_right=False
keyword:
In [127]: plt.figure()
Out[127]: <Figure size 640x480 with 0 Axes>
In [128]: df.plot(secondary_y=['A', 'B'], mark_right=False)
Out[128]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65f6102390>
Suppressing tick resolution adjustment
pandas includes automatic tick resolution adjustment for regular frequency time-series data. For limited cases where pandas cannot infer the frequency information (e.g., in an externally created twinx
), you can choose to suppress this behavior for alignment purposes.
Here is the default behavior, notice how the x-axis tick labeling is performed:
In [129]: plt.figure()
Out[129]: <Figure size 640x480 with 0 Axes>
In [130]: df.A.plot()
Out[130]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65dc39f978>
Using the x_compat
parameter, you can suppress this behavior:
In [131]: plt.figure()
Out[131]: <Figure size 640x480 with 0 Axes>
In [132]: df.A.plot(x_compat=True)
Out[132]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65dc39f1d0>
If you have more than one plot that needs to be suppressed, the use
method in pandas.plotting.plot_params
can be used in a with statement:
In [133]: plt.figure()
Out[133]: <Figure size 640x480 with 0 Axes>
In [134]: with pd.plotting.plot_params.use('x_compat', True):
.....: df.A.plot(color='r')
.....: df.B.plot(color='g')
.....: df.C.plot(color='b')
.....:
Automatic date tick adjustment
New in version 0.20.0.
TimedeltaIndex
now uses the native matplotlib tick locator methods, it is useful to call the automatic date tick adjustment from matplotlib for figures whose ticklabels overlap.
See the autofmt_xdate
method and the matplotlib documentationopen in new window for more.
Subplots
Each Series
in a DataFrame
can be plotted on a different axis with the subplots
keyword:
In [135]: df.plot(subplots=True, figsize=(6, 6));
Using layout and targeting multiple axes
The layout of subplots can be specified by the layout
keyword. It can accept (rows, columns)
. The layout
keyword can be used in hist
and boxplot
also. If the input is invalid, a ValueError
will be raised.
The number of axes which can be contained by rows x columns specified by layout
must be larger than the number of required subplots. If layout can contain more axes than required, blank axes are not drawn. Similar to a NumPy array’s reshape
method, you can use -1
for one dimension to automatically calculate the number of rows or columns needed, given the other.
In [136]: df.plot(subplots=True, layout=(2, 3), figsize=(6, 6), sharex=False);
The above example is identical to using:
In [137]: df.plot(subplots=True, layout=(2, -1), figsize=(6, 6), sharex=False);
The required number of columns (3) is inferred from the number of series to plot and the given number of rows (2).
You can pass multiple axes created beforehand as list-like via ax
keyword. This allows more complicated layouts. The passed axes must be the same number as the subplots being drawn.
When multiple axes are passed via the ax
keyword, layout
, sharex
and sharey
keywords don’t affect to the output. You should explicitly pass sharex=False
and sharey=False
, otherwise you will see a warning.
In [138]: fig, axes = plt.subplots(4, 4, figsize=(6, 6))
In [139]: plt.subplots_adjust(wspace=0.5, hspace=0.5)
In [140]: target1 = [axes[0][0], axes[1][1], axes[2][2], axes[3][3]]
In [141]: target2 = [axes[3][0], axes[2][1], axes[1][2], axes[0][3]]
In [142]: df.plot(subplots=True, ax=target1, legend=False, sharex=False, sharey=False);
In [143]: (-df).plot(subplots=True, ax=target2, legend=False,
.....: sharex=False, sharey=False);
.....:
Another option is passing an ax
argument to Series.plot()
open in new window to plot on a particular axis:
In [144]: fig, axes = plt.subplots(nrows=2, ncols=2)
In [145]: df['A'].plot(ax=axes[0, 0]);
In [146]: axes[0, 0].set_title('A');
In [147]: df['B'].plot(ax=axes[0, 1]);
In [148]: axes[0, 1].set_title('B');
In [149]: df['C'].plot(ax=axes[1, 0]);
In [150]: axes[1, 0].set_title('C');
In [151]: df['D'].plot(ax=axes[1, 1]);
In [152]: axes[1, 1].set_title('D');
Plotting with error bars
Plotting with error bars is supported in DataFrame.plot()
open in new window and Series.plot()
open in new window.
Horizontal and vertical error bars can be supplied to the xerr
and yerr
keyword arguments to plot()
open in new window. The error values can be specified using a variety of formats:
- As a
DataFrame
open in new window ordict
of errors with column names matching thecolumns
attribute of the plottingDataFrame
open in new window or matching thename
attribute of theSeries
open in new window. - As a
str
indicating which of the columns of plottingDataFrame
open in new window contain the error values. - As raw values (
list
,tuple
, ornp.ndarray
). Must be the same length as the plottingDataFrame
open in new window/Series
open in new window.
Asymmetrical error bars are also supported, however raw error values must be provided in this case. For a M
length Series
open in new window, a Mx2
array should be provided indicating lower and upper (or left and right) errors. For a MxN
DataFrame
open in new window, asymmetrical errors should be in a Mx2xN
array.
Here is an example of one way to easily plot group means with standard deviations from the raw data.
# Generate the data
In [153]: ix3 = pd.MultiIndex.from_arrays([
.....: ['a', 'a', 'a', 'a', 'b', 'b', 'b', 'b'],
.....: ['foo', 'foo', 'bar', 'bar', 'foo', 'foo', 'bar', 'bar']],
.....: names=['letter', 'word'])
.....:
In [154]: df3 = pd.DataFrame({'data1': [3, 2, 4, 3, 2, 4, 3, 2],
.....: 'data2': [6, 5, 7, 5, 4, 5, 6, 5]}, index=ix3)
.....:
# Group by index labels and take the means and standard deviations
# for each group
In [155]: gp3 = df3.groupby(level=('letter', 'word'))
In [156]: means = gp3.mean()
In [157]: errors = gp3.std()
In [158]: means
Out[158]:
data1 data2
letter word
a bar 3.5 6.0
foo 2.5 5.5
b bar 2.5 5.5
foo 3.0 4.5
In [159]: errors
Out[159]:
data1 data2
letter word
a bar 0.707107 1.414214
foo 0.707107 0.707107
b bar 0.707107 0.707107
foo 1.414214 0.707107
# Plot
In [160]: fig, ax = plt.subplots()
In [161]: means.plot.bar(yerr=errors, ax=ax, capsize=4)
Out[161]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d1048400>
Plotting tables
Plotting with matplotlib table is now supported in DataFrame.plot()
open in new window and Series.plot()
open in new window with a table
keyword. The table
keyword can accept bool
, DataFrame
open in new window or Series
open in new window. The simple way to draw a table is to specify table=True
. Data will be transposed to meet matplotlib’s default layout.
In [162]: fig, ax = plt.subplots(1, 1)
In [163]: df = pd.DataFrame(np.random.rand(5, 3), columns=['a', 'b', 'c'])
In [164]: ax.get_xaxis().set_visible(False) # Hide Ticks
In [165]: df.plot(table=True, ax=ax)
Out[165]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d0ff7550>
Also, you can pass a different DataFrame
open in new window or Series
open in new window to the table
keyword. The data will be drawn as displayed in print method (not transposed automatically). If required, it should be transposed manually as seen in the example below.
In [166]: fig, ax = plt.subplots(1, 1)
In [167]: ax.get_xaxis().set_visible(False) # Hide Ticks
In [168]: df.plot(table=np.round(df.T, 2), ax=ax)
Out[168]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d0efdcc0>
There also exists a helper function pandas.plotting.table
, which creates a table from DataFrame
open in new window or Series
open in new window, and adds it to an matplotlib.Axes
instance. This function can accept keywords which the matplotlib tableopen in new window has.
In [169]: from pandas.plotting import table
In [170]: fig, ax = plt.subplots(1, 1)
In [171]: table(ax, np.round(df.describe(), 2),
.....: loc='upper right', colWidths=[0.2, 0.2, 0.2])
.....:
Out[171]: <matplotlib.table.Table at 0x7f65d0e61b38>
In [172]: df.plot(ax=ax, ylim=(0, 2), legend=None)
Out[172]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d0eab358>
Note: You can get table instances on the axes using axes.tables
property for further decorations. See the matplotlib table documentationopen in new window for more.
Colormaps
A potential issue when plotting a large number of columns is that it can be difficult to distinguish some series due to repetition in the default colors. To remedy this, DataFrame
plotting supports the use of the colormap
argument, which accepts either a Matplotlib colormapopen in new window or a string that is a name of a colormap registered with Matplotlib. A visualization of the default matplotlib colormaps is available hereopen in new window.
As matplotlib does not directly support colormaps for line-based plots, the colors are selected based on an even spacing determined by the number of columns in the DataFrame
. There is no consideration made for background color, so some colormaps will produce lines that are not easily visible.
To use the cubehelix colormap, we can pass colormap='cubehelix'
.
In [173]: df = pd.DataFrame(np.random.randn(1000, 10), index=ts.index)
In [174]: df = df.cumsum()
In [175]: plt.figure()
Out[175]: <Figure size 640x480 with 0 Axes>
In [176]: df.plot(colormap='cubehelix')
Out[176]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d0defdd8>
Alternatively, we can pass the colormap itself:
In [177]: from matplotlib import cm
In [178]: plt.figure()
Out[178]: <Figure size 640x480 with 0 Axes>
In [179]: df.plot(colormap=cm.cubehelix)
Out[179]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d0c22a90>
Colormaps can also be used other plot types, like bar charts:
In [180]: dd = pd.DataFrame(np.random.randn(10, 10)).applymap(abs)
In [181]: dd = dd.cumsum()
In [182]: plt.figure()
Out[182]: <Figure size 640x480 with 0 Axes>
In [183]: dd.plot.bar(colormap='Greens')
Out[183]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d0a5de10>
Parallel coordinates charts:
In [184]: plt.figure()
Out[184]: <Figure size 640x480 with 0 Axes>
In [185]: parallel_coordinates(data, 'Name', colormap='gist_rainbow')
Out[185]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d08e5eb8>
Andrews curves charts:
In [186]: plt.figure()
Out[186]: <Figure size 640x480 with 0 Axes>
In [187]: andrews_curves(data, 'Name', colormap='winter')
Out[187]: <matplotlib.axes._subplots.AxesSubplot at 0x7f65d06b6518>
Plotting directly with matplotlib
In some situations it may still be preferable or necessary to prepare plots directly with matplotlib, for instance when a certain type of plot or customization is not (yet) supported by pandas. Series
and DataFrame
objects behave like arrays and can therefore be passed directly to matplotlib functions without explicit casts.
pandas also automatically registers formatters and locators that recognize date indices, thereby extending date and time support to practically all plot types available in matplotlib. Although this formatting does not provide the same level of refinement you would get when plotting via pandas, it can be faster when plotting a large number of points.
In [188]: price = pd.Series(np.random.randn(150).cumsum(),
.....: index=pd.date_range('2000-1-1', periods=150, freq='B'))
.....:
In [189]: ma = price.rolling(20).mean()
In [190]: mstd = price.rolling(20).std()
In [191]: plt.figure()
Out[191]: <Figure size 640x480 with 0 Axes>
In [192]: plt.plot(price.index, price, 'k')
Out[192]: [<matplotlib.lines.Line2D at 0x7f65da5f8710>]
In [193]: plt.plot(ma.index, ma, 'b')
Out[193]: [<matplotlib.lines.Line2D at 0x7f65d9ab9518>]
In [194]: plt.fill_between(mstd.index, ma - 2 * mstd, ma + 2 * mstd,
.....: color='b', alpha=0.2)
.....:
Out[194]: <matplotlib.collections.PolyCollection at 0x7f65d9ab9128>
Trellis plotting interface
Warning
The rplot
trellis plotting interface has been removed. Please use external packages like seabornopen in new window for similar but more refined functionality and refer to our 0.18.1 documentation hereopen in new window for how to convert to using it.
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