How do I loop through files saved in my workspace?

I have several matrices saved in my workspace whose file names differ only in a number located in the middle (eg RA_1002_timecourse, RA_893_timecourse, etc). I need to add up a given column (2) across all numbers. I have something like this (where q is the list of numbers):

o = zeros(16:1)
for z = 1:length(q)
o = o + RA_%s_timecourse(:,2),q{z};

Obviously this doesn't work but I hope you can see what I'm trying to do.

Answer 1

[Chad Greene]

It's a clunky solution, but you could save your variables in .mat files, then load them like

for k = 1:5
  load(['variableNamed',q(k),'.mat'])
end

Answer 2

[Geoff Hayes]

Hi Tom - an alternative would have been to save all of these matrices to a cell array and then you could just iterate over it (the array) to sum the second column from each matrix (I'm guessing that is what you mean to do - sum all elements from the second column of all matrices, just a little unsure why o has been defined to be a 16x1 vector):

 total = 0;
 for i=1:length(cellArray) % cellArray contains all of your matrices
   mtx = cellArray{i};
   total = total + sum(mtx(:,2));
 end

But since you have your variable names in q cell array (or just the numeric portion of it) then you could do something like the following where we build a command string and then evaluate this command:

 total = 0;

 % iterate over all variable names (or the portion of it)
 for i=1:length(q) 
   % create the matrix variable name
   varName = sprintf('RA_%s_timecourse',q{i});

   % create the command (sum the second column) to evaluate
   cmd = ['sum(' varName '(:,2))'];

   % evaluate and add to the total
   total = total + eval(cmd);
 end

Hope that the above helps!

[Tom]

I'm not trying to sum the components, I just need the individual components added to make one vector. The first solution looks like it should work but is there a command to save into a cell array? I'm trying to make a script that will do all the work for future data sets. Thanks

[Geoff Hayes]

So you want to concatenate the second column of each matrix to get one single vector.

The first solution from above can be changed to

 vctr = [];
 for i=1:length(cellArray) % cellArray contains all of your matrices
   mtx = cellArray{i};
   vctr = [vctr ; mtx(:,2)];
 end

The second solution from above can be changed similarly to

 vctr = [];
 for i=1:length(q) 
   varName = sprintf('RA_%s_timecourse',q{i});
   cmd     = [varName '(:,2)'];
   vctr    = [vctr; eval(cmd)];
 end

There may be a command to save (all?) your matrices into a cell array, but again you may just want to code something up from what you have already

 cellArray = cell(length(q),1);
 for i=1:length(q)
   varName = sprintf('RA_%s_timecourse',q{i});
   cmd     = ['cellArray{' num2str(i) '}=' varName ';'];
   eval(cmd);
 end

Answer 3

[José-Luis]

RA_1002_timecourse = rand(10);
RA_893_timecourse = rand(10);

%list variables in workspace
myVars =  whos;
myVars = {myVars(:).name};
%Finding out the ones that fullfill the condition
vals = regexp(myVars,'_[0-9]+_');
idx = cellfun(@(x) ~isempty(x) ,vals);
myVars = myVars(idx);
%Adding up the second column

%Preallocating
your_mat = zeros(size( eval(myVars{1}),1), 1);
for (ii = myVars)
    temp_mat = evalin('base',ii{:});
    your_mat = your_mat + temp_mat(:,2);
end