First time matlab user problem Matrix dimensions must agree?

Question

Azfar 2013-4-23

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Hi,

I'm a first time matlab user and I've run into a bit of a problem I keep getting an error. Here is my sequence of codes:

 derivefilter(FREQSPEC,600);
handle =
       1
y =
  173.0011
ans =
  173.0011
filtering=applyfilter(pic1,ans);  
Error using  .* 
Matrix dimensions must agree.
Error in applyfilter (line 3)
filteredspec=imgspec.*filter;

Here is the script "applyfilter":

function y=applyfilter(img,filter)
imgspec=fftshift(fft2(img));
filteredspec=imgspec.*filter;
y=real(ifft2(fftshift(filteredspec)));

Any help would be appreciated thanks.

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Answer 1

Image Analyst 2013-4-23

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What does derivefilter() return? You're not accepting any matrix for the filter that you can then pass in to applyfilter() instead of ans. You may need to have something like

myFilter = derivefilter(FREQSPEC,600);
filtering=applyfilter(pic1, myFilter);

but we can't tell until we know what's inside derivefilter().

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Walter Roberson 2013-4-24

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pic1 = rgb2gray(pic1); %convert to 600x600

but you also need to solve the other issues.

Azfar 2013-4-24

Thanks for your help, re-sizing the pic1 variable resolved the issue.

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Answer 2

Leah 2013-4-23

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imgspec and filter must have the same dimension to do a element-wise multiplications

size(imspec)
size(filter)

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Answer 3

Jan 2013-4-23

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编辑：Jan 2013-4-23

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Your code would be easier to read, if you spend the time for reading the manuals for this forum and format the code properly.

It looks like:

imgspec .* filter

cannot work, because the array sizes do not match. This is surprising, because the value of filter seems to be a scalar.

Using ans explicitly is a bad idea, because this value is very volatile and debugging can change the value. filter is not a good choice also, because this is a name of an important built-in function.

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Azfar 2013-4-23

Thanks for the response, how exactly would I go about resolving this situation?

The scripts I use are laid out by my supervisor for my project. So I have to adhere to his methodology.

Jan 2013-4-24

@Azfar: Then it is the job of your supervisor to find the solution. We cannot guess how this should be fixed, because all we see is the failing code. To find a solution, one has to know the intention of the code, but wrong code cannot carry this kind of information.

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