How to access/manipulate data from cell arrays?

Question

Thomas Veith 2019-6-3

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465317-how-to-access-manipulate-data-from-cell-arrays

评论： Adam Danz 2019-6-3

So I have the code bleow which sovles an ODE 1000 times with random variables. The result is a 1000 by 1 cell array, the contents of which are all XX by 2 numeric arrays (column 1 solves x(1), column 2 solves x(2)). What I would like to produce is an XX by 1000 numeric array, where my 1000 columns would be comprised of all column 2 data from the numeric arrays nested in my cell array. Is this possible? I've looked through the Cell Arrays and Multilevel Indexing to Access Parts of Cells pages, and haven't been able to find what I'm looking for. Any help would be appreciated.

n = 1000;
result = cell(n,1);
for k=1:n
    tspan=[1 7];A0=rand;P0=rand;g=rand;p=rand;B=rand;
    [t,x] = ode45(@(t,x) [-g*x(1) + p*x(1); -x(1)*x(2)+ B*x(2)], tspan, [A0 P0]);
    result{k} = x;
end

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Adam Danz 2019-6-3

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465317-how-to-access-manipulate-data-from-cell-arrays#answer_377635

编辑：Adam Danz 2019-6-3

This extracts column 2 data from all elements of the cell array and arranges it in a row within a cell array as you described.

C = cellfun(@(x)x(:,2),result,'UniformOutput', false)';

Here's how to put that into a padded array

% how much padding is needed per cell?
maxLen = max(cellfun(@(x)size(x,1),result)); %max length
padNum = maxLen - cellfun(@(x)size(x,1),result); 
% get the col 2 vals and pad them
C = cellfun(@(x)x(:,2),result,'UniformOutput', false); 
Cpad = cellfun(@(x,p)padarray(x,p,NaN,'post'),C,num2cell(padNum),'UniformOutput',false);
% Put them into a matrix
M = cell2mat(Cpad');

4 个评论
显示 2更早的评论隐藏 2更早的评论

Thomas Veith 2019-6-3

Thank you! What if they were all the same size? I get that I could write a matrix M123=[C{1,1},C{1,2},C{1,3},...,C{1,1000}]; but that would be quite tedious.

Adam Danz 2019-6-3

If they were all the same size, it would be as easy as

C = cellfun(@(x)x(:,2),result,'UniformOutput', false)'; 
cell2mat(C)

请先登录，再进行评论。

Answer 2

madhan ravi 2019-6-3

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/465317-how-to-access-manipulate-data-from-cell-arrays#answer_377636

编辑：madhan ravi 2019-6-3

result{k} = x(:,2);

To produce a numeric matrix you need to append with nan or zeros at the end.

M=max(cellfun('prodofsize', result));
Desired=cell2mat(cellfun(@(x) [x;zeros(M-numel(x),1)], result,'un', 0))

2 个评论
显示无隐藏无

Thomas Veith 2019-6-3

Thank you for your quick reply! That works very well, however, it's not exactly what I was looking for. That changes my result so that my cell array only includes the results from column 2, each selection of which represents a numerica array of varying size (41x1, 285x1, etc, etc). That is nice, and more managable than including both x solutions, but, what I was really hoping for was that I could produce a YYx1000 numeric array, so that column one would be the 41 entries, column two the 285 entries, etc, etc. Is this possible? Thanks in advance.