Accessing matrix columns using index which are not continuous (example:index=1,5,9,13 etc)

I have a matrix say R which is having columns corresponding to some variable & text files each of which also contains a column.I have to read these text files corresponding to each column of the matrix R which are not in sequence.For example I have to read text file 1.txt for columns 1,5,7,8 and 2.txt for 2,9,11,14 .How can I do it using for or some other loop? Thanks in advance.

Answer 1

[Guillaume]

I'm not clear on what exactly is posing you problem and not clear either on the structure of your text files, so can only give you generic advice:

Assumption: you have a cell array, let's call it columnorder, which tell you the origin of each column of R. e.g.:

columnorder = {[1 5 7 8], [2 9 11 14], [3 4 6 10 12 13]};

tells you that column 1 5 7 8 come from column 1:4 pf the first file, 2 9 11 14 come from column 1:4 of the second file and column 3 10 4 12 6 13 come from column 1:6 of the third file. Note that I shuffled the order of the columns from that third file on purpose.

assert(sort([columnorder{:}]) == 1:max([columnorder{:}]), 'some columns are missing or duplicate');
R = zeros(someheight, max([columnorder{:}])); %destination
for fileidx = 1:numtextfile
   filedata = csvread(sprintf('%d.txt', fileidx)); %or however you read the file
   R(:, columnorder{fileidx}) = filedata(:, 1:numel(columnorder{fileidx}));
end