Convert char array to single element Matlab

Question

I am retrieving file names of Images in a array as:

image_files = dir(strcat(dir_path, '\*' , img_extension));
s = image_files(j).name

Now I need to save names of images files in a file, but first I need to concatenate all the image names in a single matrix,

M = [M, s]

However since s is a character array, all the characters of file names will be treated as separate columns where as I need to treat a single file name as a single entity in M.

Is there any work around?

Try this maybe - {image_files.name}. It produces a cell array, if you are okay with it. — Divakar
– Divakar, Commented Mar 25, 2014 at 8:05
@Divakar then i wont be able to write this matrix, M, to a text file using dlmwrite() function.... is there any other way to write M to a text file even if it contains cell array elements.... thanks — Zohaib
– Zohaib, Commented Mar 25, 2014 at 8:07
dlmwrite doesn't support strings, only numeric data (the fact that it apparently happens to work with char arrays is an undocumented feature) - you'd be far better off using a cell array of strings. — Notlikethat
– Notlikethat, Commented Mar 25, 2014 at 9:39

Divakar · Accepted Answer · 2014-03-25 09:53:21Z

1

Try this for PNG files in the working directory -

%%// Parameters
img_extension = '.png';
dir_path = pwd;
textfile = 'myFile.csv';

image_files = dir(strcat(dir_path,filesep,'*',img_extension));
x = {image_files.name};

fid=fopen(textfile,'wt');
[rows,cols]=size(x);
for i=1:rows
    %fprintf(fid,'%s,',x{i,1:end-1}); %%// Use comma separated file names
    fprintf(fid,'%s\n',x{i,1:end-1}); %%// Use newline separated file names
    fprintf(fid,'%s\n',x{i,end});
end
fclose(fid);

Edit 1: If you still need a char matrix or char arrays of the file names, choose from one of the following three outputs -

x = {image_files.name};
char_matrix1 = char(x{:}) %%// Create a MxN char matrix
char_array1  = strjoin(x,',') %%// Create a Mx1 char matrix separated by commas between filenames
char_array2  = strjoin(x,' ') %%// Create a Mx1 char matrix separated by spaces between filenames

Note : strjoin is available in the recent MATLAB version and on MATLAB file-exchange here.

edited Mar 25, 2014 at 9:53

answered Mar 25, 2014 at 8:10

Divakar

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3 Comments

Zohaib Over a year ago

Hi Divakar, it seems a good solution , however not applicable in my scenario, thanks...

Divakar Over a year ago

@Zohaib Try the Edit 1.

Notlikethat Over a year ago

Just use filesep (or fullfile) to construct platform-independent paths, not that nasty if-else setup.

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