matlab iterative filenames for saving

Question

this question about matlab: i'm running a loop and each iteration a new set of data is produced, and I want it to be saved in a new file each time. I also overwrite old files by changing the name. Looks like this:

name_each_iter = strrep(some_source,'.string.mat','string_new.(j).mat')

and what I#m struggling here is the iteration so that I obtain files: ...string_new.1.mat ...string_new.2.mat etc.

I was trying with various combination of () [] {} as well as 'string_new.'j'.mat' (which gave syntax error)

How can it be done?

Answer 1

For creating a name based of an already existing file, you can use regexp to detect the '_new.(number).mat' and change the string depending on what regexp finds:

original_filename = 'data.string.mat';
im = regexp(original_filename,'_new.\d+.mat')
if isempty(im) % original file, no _new.(j) detected
    newname = [original_filename(1:end-4) '_new.1.mat'];
else
    num = str2double(original_filename(im(end)+5:end-4));
    newname = sprintf('%s_new.%d.mat',original_filename(1:im(end)-1),num+1);
end

This does exactly that, and produces:

    data.string_new.1.mat
    data.string_new.2.mat
    data.string_new.3.mat
    ...

    data.string_new.9.mat
    data.string_new.10.mat
    data.string_new.11.mat

when iterating the above function, starting with 'data.string.mat'

Answer 2

Strings are just vectors of characters. So if you want to iteratively create filenames here's an example of how you would do it:

for j = 1:10,
   filename = ['string_new.' num2str(j) '.mat'];
   disp(filename)
end

The above code will create the following output:

string_new.1.mat
string_new.2.mat
string_new.3.mat
string_new.4.mat
string_new.5.mat
string_new.6.mat
string_new.7.mat
string_new.8.mat
string_new.9.mat
string_new.10.mat

Answer 3

You could also generate all file names in advance using NUM2STR:

>> filenames = cellstr(num2str((1:10)','string_new.%02d.mat'))

filenames = 
    'string_new.01.mat'
    'string_new.02.mat'
    'string_new.03.mat'
    'string_new.04.mat'
    'string_new.05.mat'
    'string_new.06.mat'
    'string_new.07.mat'
    'string_new.08.mat'
    'string_new.09.mat'
    'string_new.10.mat'

Now access the cell array contents as filenames{i} in each iteration

Answer 4

sprintf is very useful for this:

for ii=5:12
    filename = sprintf('data_%02d.mat',ii)
end

this assigns the following strings to filename:

    data_05.mat
    data_06.mat
    data_07.mat
    data_08.mat
    data_09.mat
    data_10.mat
    data_11.mat
    data_12.mat

notice the zero padding. sprintf in general is useful if you want parameterized formatted strings.