ggplot2 绘制日期数据时出错 - 需要 TRUE/FALSE 时缺少值
我正在尝试绘制一些从外部来源获取的成绩。日期格式看起来像这样：
2011-08-23T17:07:05
所以我用 strptime(date, "%FT%X") 解析它并得到 POSIXlt。我最终得到一个完整的数据框，如下所示：
date subject grade
1 2011-08-23 17:07:05 AP Biology 95.83
2 2011-08-24 17:07:03 AP Biology 95.83
3 2011-08-25 17:08:27 AP Biology 95.83
4 2011-08-17 17:05:54 US History 157.14
5 2011-08-18 17:05:24 US History 157.14
6 2011-08-19 17:05:35 US History 157.14
7 2011-08-22 17:06:25 US History 157.14
8 2011-08-23 17:07:05 US History 157.14
9 2011-08-24 17:07:03 US History 157.14
10 2011-08-25 17:08:27 US History 157.14
11 2011-08-19 17:05:35 Yearbook 0.00
12 2011-08-22 17:06:25 Yearbook 0.00
13 2011-08-23 17:07:05 Yearbook 100.00
14 2011-08-24 17:07:03 Yearbook 100.00
15 2011-08-25 17:08:27 Yearbook 100.00
具有以下结构：
'data.frame': 15 obs. of 3 variables:
$ date : POSIXlt, format: "2011-08-23 17:07:05" "2011-08-24 17:07:03" ...
$ subject: Factor w/ 3 levels "AP Biology","US History",..: 1 1 1 2 2 2 2 ...
$ grade : num 95.8 95.8 95.8 157.1 157.1 ...
当我尝试绘制此数据时：
> ggplot(data=grades, aes(date, grade, factor=subject)) + geom_line()
Error in if (length(range) == 1 || diff(range) == 0) { :
missing value where TRUE/FALSE needed
我不知道我在这里做错了什么。我通过这样做将其范围缩小到日期处理：
ggplot(data=grades,
aes(seq(length(grades[,1])),
grade, color=subject)) + geom_line()
...但是如何正确进行日期处理？
I'm trying to plot some grades I'm pulling from an external source. The date format comes in looking like this:
2011-08-23T17:07:05
So I parse it with strptime(date, "%FT%X") and get a POSIXlt. I end up with a complete data frame that looks like this:
date subject grade
1 2011-08-23 17:07:05 AP Biology 95.83
2 2011-08-24 17:07:03 AP Biology 95.83
3 2011-08-25 17:08:27 AP Biology 95.83
4 2011-08-17 17:05:54 US History 157.14
5 2011-08-18 17:05:24 US History 157.14
6 2011-08-19 17:05:35 US History 157.14
7 2011-08-22 17:06:25 US History 157.14
8 2011-08-23 17:07:05 US History 157.14
9 2011-08-24 17:07:03 US History 157.14
10 2011-08-25 17:08:27 US History 157.14
11 2011-08-19 17:05:35 Yearbook 0.00
12 2011-08-22 17:06:25 Yearbook 0.00
13 2011-08-23 17:07:05 Yearbook 100.00
14 2011-08-24 17:07:03 Yearbook 100.00
15 2011-08-25 17:08:27 Yearbook 100.00
With the following structure:
'data.frame': 15 obs. of 3 variables:
$ date : POSIXlt, format: "2011-08-23 17:07:05" "2011-08-24 17:07:03" ...
$ subject: Factor w/ 3 levels "AP Biology","US History",..: 1 1 1 2 2 2 2 ...
$ grade : num 95.8 95.8 95.8 157.1 157.1 ...
When I try to plot this data:
> ggplot(data=grades, aes(date, grade, factor=subject)) + geom_line()
Error in if (length(range) == 1 || diff(range) == 0) { :
missing value where TRUE/FALSE needed
I don't know what I'm doing wrong here. I narrowed it down to the date handling by doing this:
ggplot(data=grades,
aes(seq(length(grades[,1])),
grade, color=subject)) + geom_line()
... but how do I do the date handling correctly?
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ggplot2 仅支持 POSIXct 类的时间。 POSIXct 类将自 1970 年初（UTC 时区）以来的（有符号）秒数表示为数值向量。
POSIXlt类是表示九个元素（sec、min、hour等）的向量命名列表。您可以使用以下内容：
Only times of class
POSIXctare supported in ggplot2. ClassPOSIXctrepresents the (signed) number of seconds since the beginning of 1970 (in the UTC timezone) as a numeric vector. ClassPOSIXltis a named list of vectors representing nine elements (sec,min,hour, etc.).You can use the following:
我想我已经明白了这一点。区别在于对
POSIXct与POSIXlt的理解。POSIXlt是部分日历时间。POSIXct是自纪元以来的秒数。strptime返回一个 `POSIXct为了使用此数据，我需要转换时间戳：
I think I've figured this out. The difference is in understanding
POSIXctvs.POSIXlt.POSIXltis the calendar time in parts.POSIXctis the number of seconds since the epoch.strptimereturns a `POSIXctIn order to use this data, I need to convert the timestamps: