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Resize a matrix into another with different size

Asked by Tiago Dias on 26 Nov 2018
Latest activity Edited by Stephen Cobeldick on 26 Nov 2018
Hello, i got a matrix X and I want to transform X into a matrix rows x collumns, in this case into a 4 by 7 matrix. I used reshape but it doesnt work because of the 2 nans i must create i assume.
k = 26;
X = [1:k]';
[n,m] = size(X);
rows = 4;
columns = ceil(n/rows);
Into something like that, if possible:
x(1) x(5) x(9) x(13) x(17) x(21) x(25)
x(2) x(6) x(10) x(14) x(18) x(22) x(26)
x(3) x(7) x(11) x(15) x(19) x(23) NaN
x(4) x(8) x(12) x(16) x(20) x(24) NaN

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3 Answers

Answer by Matt J
on 26 Nov 2018
Edited by Matt J
on 26 Nov 2018
 Accepted Answer

extra = rows*ceil(numel(X)/rows) - numel(X);
reshape([X(:);nan(extra,1)],rows,columns)

  3 Comments

this one doesnt work
Error using horzcat
Dimensions of matrices being concatenated are not consistent.
Error in ES5 (line 25)
reshape([X(:),nan(extra,1)],rows,columns)
([X(:);nan(extra,1)]
^ needs a semicolon here!
Thanks for your help!

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Answer by Luna
on 26 Nov 2018
Edited by Luna
on 26 Nov 2018

Hi,
Try this:
k = 26;
X = [1:k]';
[n,m] = size(X);
rows = 4;
columns = ceil(n/rows);
X(numel(X):(rows*columns)) = NaN;
reshape(X,rows,columns)

  1 Comment

this one works 95% i would say, the number 26 doesnt show up :/
ans =
1 5 9 13 17 21 25
2 6 10 14 18 22 NaN
3 7 11 15 19 23 NaN
4 8 12 16 20 24 NaN
I tried this and i think it works
extra_row = rows * columns;
X(n+1:extra_row) = NaN;
X_new = reshape(X,rows,columns)

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Answer by Stephen Cobeldick on 26 Nov 2018
Edited by Stephen Cobeldick on 26 Nov 2018

A simpler solution:
>> X = 1:26;
>> R = 4;
>> N = numel(X);
>> M = nan(R,ceil(N/R));
>> M(1:N) = X
M =
1 5 9 13 17 21 25
2 6 10 14 18 22 26
3 7 11 15 19 23 NaN
4 8 12 16 20 24 NaN

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