# MATLAB: Storing multiple value in array without overriding.

array

Below is the code snippet, where I am selecting images one by one, converting a image in 30*30 patch and calculating the standard deviation of patch and then storing that value in excel sheet. But the problem is only the standard deviation of last image is being saved to excel sheet others value are getting over ridden. How to avoid that?
``Directory = 'With MA\';%Imgs = dir(fullfile(Directory,'*.jpg'));Imgs = dir(Directory);nfiles = length(Imgs);    % Number of files foundfor z=1:nfiles    thisname = Imgs(z).name;    thisfile = fullfile(Directory, thisname);    try      Img = imread(thisfile);               %Img = imread(fullfile(Directory,Imgs(z).name));   I=Img(:,:,2);   imSz = size(I);    patchSz = [30 30];    xIdxs = [1:patchSz(2):imSz(2) imSz(2)+1];    yIdxs = [1:patchSz(1):imSz(1) imSz(1)+1];    patches = cell(length(yIdxs)-1,length(xIdxs)-1);%for patches    stan = cell(length(yIdxs)-1,length(xIdxs)-1);%for standard deviation        for i = 1:length(yIdxs)-1    Isub = I(yIdxs(i):yIdxs(i+1)-1,:);    for j = 1:length(xIdxs)-1        patches{i,j} = Isub(:,xIdxs(j):xIdxs(j+1)-1);%saving patches        stan{i,j} = std2(patches{i,j});%saving standard deviation    end    end            catch    end    xlswrite('output.xlsx', stan); end``

``...for z=1:nfiles     ...     F = sprintf('output_%d.xlsx',z);     xlswrite(F,...); end``
``[~,N] = fileparts(thisname);F = sprintf('%s.xlsx',N);``