MATLAB: How to extract information from the name of a file without using strsplit function

strsplit

Hello!

I need some help extracting some coordenates from the name of a a file.

I have 224 files named like this: files=[{' x+0.000mm_y_+0.000mm_z_+0.000mm.dat_ '},….].

I want to extract the X coordenate and the Y coordenate (in this case 0.000 both) and finally have a matrix of 224×2 (224 rows for each file (files are points), and 2 columns for x and y).

I can not use strsplit function because i am using Matlab2010. I have tried with regexp:

    delim = '[mm+]';
    coord = regexp(files,delim, 'split');

but then i obtain a cell array 224×1 awith cells of 1×10 inside an i do not know how to work with it.

Any idea?? I would really appreciate your help.

Thanks!!

Best Answer

files=[{' x+0.000mm_y_+0.000mm_z_+0.000mm.dat_ '}  {' x+10.000mm_y_+20.000mm_z_+30.000mm.dat_ '}]
coord = regexp(files,'\d+(\.\d+)?','match')
coord=cell2mat(cellfun(@str2double,coord,'un',0)')

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files = {' x+0.000mm_y_+0.000mm_z_+0.000mm.dat_ ', ...
         ' x+5.000mm_y_+10.000mm_z_+0.000mm.dat_ ', ...
         ' x+10.000mm_y_+20.000mm_z_+30.000mm.dat_ ', ...
         ' x+15.000mm_y_+40.000mm_z_+0.000mm.dat_ ', ...
         ' x+20.000mm_y_+60.000mm_z_+0.000mm.dat_ '}
coordC = regexp(files,'\d+(\.\d+)?','match');
coord  = cat(1, coords{:});

Reply:

    '0.000'     '0.000'     '0.000' 
    '5.000'     '10.000'    '0.000' 
    '10.000'    '20.000'    '30.000'
    '15.000'    '40.000'    '0.000' 
    '20.000'    '60.000'    '0.000'

This exactly the same order as the list of file names. Therefore I do not understand the question. Please post, what you observe.

MATLAB: HELP with Undefined variable, size of the indicated variable changes with each loop iteration.

The error is Undefined function or variable 'files'. files is defined inside your for loop. So if it is undefined after the loop that means your loop didn't execute. The only reason for your loop not to execute is that length(file_data) is 0, i.e. no file was found.

Morale of the story: when interacting with the filesystem (or any data outside your program control, like user input), always check that you're getting what you're expecting. In this case, do check that there is at least one file.

Note: You don't need a loop to transform the structure returned by dir into a cell array of filenames:

files = {file_data.name};

works just as well. It would also have avoided the undefined variable error in regexp (which would just have returned an empty cell array. Most likely, another error would occur later because you haven't designed your code to cope with no file being found.

Best Answer

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