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# Why this function return empty matrix?

Asked by Ahmed almansory on 30 May 2013
```    note : the output of program is true without function
% This function take an image then devide it into block
% then reshape each block to culumn vector and put it as
% new column in new matrix(output of function).
function N=Div(m);
[rows columns ] = size(m);
%prompt the user to input the size of rows & colums in block
prompt = {'Enter block row size:','Enter block column size:'};
dlg_title = 'Input size of the block';
num_lines = 1;
def = {'8','8'};
%assign the user values to another variables
blockrow=val;
blockcolumn=val;
wholeBlockRows = floor(rows / blockrow);
blockVectorR = [blockrow * ones(1, wholeBlockRows), rem(rows, blockrow)];
wholeBlockCols = floor(columns / blockcolumn);
blockVectorC = [blockcolumn * ones(1, wholeBlockCols), rem(columns, blockcolumn)];
%convert the image into blocks
mCell = mat2cell(m, blockVectorR, blockVectorC);%now mCell contain all blocks
%convert each block to column vector then put the column vector as a column in new matrix n
t=1;
%intilizing of n
n=uint8(zeros(val*val,(rows*columns)/(val*val)));
for i=1:rows/blockrow
for j=1:rows/blockrow
thisBlock = mCell{i,j};
columnVector = thisBlock(:);
n(:,t)=columnVector;
t=t+1;
end
end
% return the new matrix
N=n;```

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Answer by Iain on 30 May 2013

Because val is not what you think it is. - It is probably 0.

## 1 Comment

Ahmed almansory on 30 May 2013

val not zero ,user determine the value of val

if we remove the first and last line of function the program is true

thank you for replay