List of specific files in a directory using `dir` command in matlab

Question

This questions is regarding dir command in matlab.

PREAMBLE

I have a set of files: 01.dat, 02.dat, 03.dat, ..., 20.dat. When I type in command line: dir('*.dat'), I will see all my files. If I want to pick only particular files in the range [01-09], I will type dir('0*.dat').

QUESTION

Suppose, I need to pick only those files, which are in the specific range, namely: 03.dat, 04.dat, 05.dat, 06.dat. How can I do it with dir?

I need something like dir('0[3:6].dat'). I want to avoid using a=dir('*.dat'); a(3:6).name; due to some reasons related to the data set. So, I want to specify the desired range at the level of "dir" command only. Any suggestions? Many thanks in advance!!

Answer 1

The function dir could be associated with arrayfun: it will apply a dir command to each member of a vector, for instance 3:6. Here, filenames will refer to four files from 03.dat to 06.dat.

Pseudo-code dir('0[3:6].dat') could be translated by:

filenames = arrayfun(@(x) dir(['0' num2str(x) '.dat']), 3:6);

Answer 2

You can use regular expressions in MATLAB to filter out what you want. It's not perfect, but gives decent results.

The following code pulls out the 03.dat, 04.dat, 05.dat, 06.dat files:

listing = dir('*.dat');
pattern = '0[3-6].dat';

% this is kind of crude, but works: use regexp then pull out all the
% non-matching ones with a call to isempty(...)
notMatching = cellfun(@isempty, regexp({listing.name}, pattern))

% Pull out the the ones that match:
betterListing = listing(~notMatching)