Undefined Variable error for a variable that is already defined?

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Natha Davis 2020-7-24

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https://ww2.mathworks.cn/matlabcentral/answers/570079-undefined-variable-error-for-a-variable-that-is-already-defined

评论： Arthur Roué 2020-7-24

Hello all,

I have this code that I have been running to process DICOM images. I previously used it to process two folders (with the same folder structure, just diff name) successfully. Now all of a sudden I get this error "Unrecognized function or variable 'a'. Error in PrintProtocol (line 82) for i=1:size(a,1)". PrintProtocol is a function written by a mentor and I am not the author.

Going to line 82 of PrintProtocol I see this: "for i=1:size(a,1)

cd([foldersin{1} imgfolder slash a(i).name]);"

'a' is defined above in line 60 as "for i=1:size(d,1)

if (d(i).isdir == 1 && length(d(i).name) > 2)

a(l,1) = d(i,1);".

I am confused why it would work previously and then stop working now. To me a is defined in line 60, but am I missing something? I am happy to provide additional details. Thank you for your help.

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Fangjun Jiang 2020-7-24

It is inside an "if" statement. It may not be assigned if condition is not met. Put a break point on line 82 and run it again to check the value of a.

Natha Davis 2020-7-24

I put a breakpoint at line 60 and I am still seeing it saying a is an unknown variable. Is there something different I should be doing to define a? I looked above and 'l=1', but I don't see anywhere it specifically says "a=" so maybe a isn't really defined. But if that is true, why did this work for 2 other folders?

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