strfind issue

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Robbie 2011-11-29

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采纳的回答： Matt Tearle

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Hi,

I have a filename (including whole path) as a string with directories separated by / e.g. root/folder/file.

I am using strfind to find the slashes as follows and to give an index array of the position of the / symbols, :

      % Find all occurances of the string '/'
      [no_slash] = strfind ( line, '/' );

and then trying to extract the filename as a string as follows:

      % Extract the case number:
      caseNo = ( [no_slash(3)+1 : no_slash(3)+4] );

I get NaN returned and I don't know why! If anyone has an idea or an alternative method then it would be much appreciated!!

Thanks,

Robbie

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Answer 1

Matt Tearle 2011-11-29

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As Daniel says, there must be more going on. Can you copy the code directly? strfind returns the indices; if there are no matches, it returns []. Hence, if line was 'root/folder/file', strfind(line,'/') returns [5,12].

So in this case you'd get an indexing (out of bounds) error on the next line. If there was three slashes in the string, you'd get a vector like [13, 14, 15, 16].

Are you perhaps trying to extract a portion of the string and str2num it? In which case, you want

caseNo = str2double(line(no_slash(3)+1 : no_slash(3)+4))

(Note: if you leave out the line in the above command, you get NaN. Or if line isn't a string.)

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Daniel Shub 2011-11-29

Good call on the str2double returning NaN.

Robbie 2011-11-29

Yeah I got it working by adding in the 'line' thanks for your help it is much appreciated.

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Answer 2

Daniel Shub 2011-11-29

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The only way

[no_slash(3)+1 : no_slash(3)+4]

can be equal to NaN is if no_slash(3) is equal to NaN. You are not showing us something important because I am pretty sure that strfind does not return NaN.

All that said fileparts might help you out...

doc fileparts

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Daniel Shub 2011-11-29

What is no_slash equal to? Can you check that line is also a string. Please post a MWE with what line needs to be to get the error?

Robbie 2011-11-29

Thanks, I got it working from matt's suggestion (I left out the line) and it works fine now, I also got it working through fileparts. Your help is much appreciated:

caseNo = line(no_slash(3)+1 : no_slash(3)+4)

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