如何在 MATLAB 中将不同长度的单元累积到矩阵中？

发布于 2024-09-06 01:38:09 字数 406 浏览 3 评论 0原文

所以，我有一个由不同长度的 1xN 向量组成的元胞数组。我想将它们附加到一个矩阵中，以便我可以使用 imagesc 显示它们。显然矩阵必须是最大向量的宽度。我当前的代码如下：

tcell = {[1,2,3], [1,2,3,4,5], [1,2,3,4,5,6], [1], []};
lens = cellfun('length', tcell);
rmat = NaN(length(tcell), max(lens));
for i = 1:length(tcell)
    rmat(i, 1:lens(i)) = tcell{i};
end

有谁知道此类问题的矢量化解决方案？由于 MATLAB 的 JIT，我并不真正担心这个循环的速度。我只是想扩展我的知识，这是我在编程中经常遇到的情况。

原文

So, I have a cell-array of 1xN vectors of different lengths. I want to append them into a matrix so I can display them with imagesc. Obviously the matrix must be the width of the largest vector. My current code for this is below:

tcell = {[1,2,3], [1,2,3,4,5], [1,2,3,4,5,6], [1], []};
lens = cellfun('length', tcell);
rmat = NaN(length(tcell), max(lens));
for i = 1:length(tcell)
    rmat(i, 1:lens(i)) = tcell{i};
end

Does anyone know a vectorized solution for this type of problem? I'm not really worried about the speed of this loop because of MATLAB's JIT. I'm just trying to expand my knowledge and this is a case that I come across quite often in my programming.

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秋心╮凉 2024-09-13 01:38:09

这是一种使用 cellfun 的解决方案匿名函数首先用 NaN 值，然后 vertcat 将单元格内容放入矩阵中：

tcell = {[1 2 3], [1 2 3 4 5], [1 2 3 4 5 6], [1], []};  % Sample cell array

maxSize = max(cellfun(@numel, tcell));               % Get the maximum vector size
fcn = @(x) [x nan(1, maxSize-numel(x))];             % Create an anonymous function
rmat = cellfun(fcn, tcell, 'UniformOutput', false);  % Pad each cell with NaNs
rmat = vertcat(rmat{:});                             % Vertically concatenate cells

输出：

rmat =

     1     2     3   NaN   NaN   NaN
     1     2     3     4     5   NaN
     1     2     3     4     5     6
     1   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN   NaN

Here's one solution that uses cellfun with an anonymous function to first pad each cell with NaN values, then vertcat to put the cell contents into a matrix:

tcell = {[1 2 3], [1 2 3 4 5], [1 2 3 4 5 6], [1], []};  % Sample cell array

maxSize = max(cellfun(@numel, tcell));               % Get the maximum vector size
fcn = @(x) [x nan(1, maxSize-numel(x))];             % Create an anonymous function
rmat = cellfun(fcn, tcell, 'UniformOutput', false);  % Pad each cell with NaNs
rmat = vertcat(rmat{:});                             % Vertically concatenate cells

And the output:

rmat =

     1     2     3   NaN   NaN   NaN
     1     2     3     4     5   NaN
     1     2     3     4     5     6
     1   NaN   NaN   NaN   NaN   NaN
   NaN   NaN   NaN   NaN   NaN   NaN

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