Fixing an eroor in simple if-function

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David 2020-4-8

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关闭： MATLAB Answer Bot 2021-8-20

Hi everyone,

I got a problem with an if-else function. I want to put the correct 4x2 matrix so here is my function:

function matrix(n)
if size(n)== 4 2
    fprintf(' Congrats \n')
else 
    fprintf(' Incorrect!!Please input a 4x2 matrix \n')
end

The problem I am facing is that whatever matrix I input they all show that INCORRECT!! PLEASE INPUT A 4X2 MATRIX, even when i input 4x2 matrix, i encounter same problem. Can anyone help me? I think the problem is at size(n)== 4 2

Thanks you

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Answer 1

Geoff Hayes 2020-4-8

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David - yes the problem is with your condtion. Note that size will return an array where each element is the size of the dimension. Trying to compare this to 4 2 will result in an Unexpected MATLAB expression error (at least it does for me) so you need to think of an alternative way to do this check. From size, you can get the number of rows and the number of columns by supplying the appropriate dimension input.

numberOfRows = size(n,1);
numberOfColumns = size(n,2);

Now that you know the size of each dimension, you can then do the appropriate comparison

if size(n,1) == 4 && size(n,2) == 2
    % congrats...
end

One further check that you may want to add is to ensure that the number of dimensions is two (since a 4x2x3 matrix will pass the above condition). See ndims for details.