How to access double arrays in a cell array?

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MiauMiau 2016-6-11

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https://ww2.mathworks.cn/matlabcentral/answers/289411-how-to-access-double-arrays-in-a-cell-array

评论： Stephen23 2016-6-12

采纳的回答： Stephen23

Hi everyone,

I have a 1x5 cell array, where each of these 5 columns contains a 20x1 double array.

Now I have the following two questions:

How can I for instance access from this cell array, the first two rows of all the double array it contains (such that I would ideally end up with a 2x5 array of doubles)?
Is there any easy way to construct from this cell array a 20x5 array of doubles, where all rows but the i-th are set to zero?

Many many thanks

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Answer 1

Stephen23 2016-6-11

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https://ww2.mathworks.cn/matlabcentral/answers/289411-how-to-access-double-arrays-in-a-cell-array#answer_225191

编辑：Stephen23 2016-6-11

在 MATLAB Online 中打开

Here are two solutions to your two tasks. First create some fake data:

>> fun = @()randi(9,20,1);
>> C = {fun(),fun(),fun(),fun(),fun()};

1. first two rows of each numeric array:

>> N = 2; % pick the number of rows
>> cell2mat(cellfun(@(c)c(1:N,:),C,'Uni',0))
ans =
     8     6     4     7     4
     9     1     4     3     8

2. All rows except the Nth are zero:

>> tmp = cell2mat(C);
>> R = 4; % pick the row
>> tmp(R~=(1:size(tmp,1)),:) = 0
tmp =
   0     0     0     0
   0     0     0     0
   0     0     0     0
   9     8     7     5
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0
   0     0     0     0

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MiauMiau 2016-6-11

many many thanks, your answers were really helpful. In the case of 2., is it possible to do the same thing (setting everything except a particular row to zero), while keeping the original format (the 1x5 cell)?