Generate new file w/ each iteration of for loop. Problem of same output in each new file?

Hi,

I'm trying to design a for loop that takes 100 random rows from a sample data set, and saves that into a new output file, one hundred times. I can get all of the output files, but each file contains the same row values. I'm not sure where the problem is?

Here's my code:

    thissample = xlsread('~/Documents/mdd_with_anx.xls');
    sampSets = 1;
    randSampNum = 1;
    for sampSets = 1:100;
        N = 100;
        c=randperm(length(thissample),N);
        randSampSet=thissample(c,:);
        for randSampNum = 1:100
            filename = ['randSamp' num2str(randSamp) '.csv'];
            csvwrite(filename,randSamp);
            randSampNum = randSampNum + 1;
        end;
        sampSets = sampSets + 1;
    end;

[Ced]

Where do you assign a value to randSamp? Also, you probably meant to write

filename = ['randSamp' num2str(randSampNum) '.csv'];

On a sidenote, the initialization of sampSets = 1 and randSampNum = 1 is not necessary. What you are essentially doing is first initialize it as a scalar (1), and then re-define it as a vector in the for loop (e.g. sampSets = 1:100)

Also, sampSets = sampSets + 1 is not necessary, same for randSampNum = randSampNum + 1.

A simple for loop looks like this:

for i = 1:10
sprintf('This is iteration: %i \n',i)
end

This would return

This is iterations: 1
This is iterations: 2
This is iterations: 3
This is iterations: 4
This is iterations: 5
This is iterations: 6
This is iterations: 7
This is iterations: 8
This is iterations: 9
This is iterations: 10

Answer 1

[Voss]

thissample = xlsread('~/Documents/mdd_with_anx.xls');
thissample_size = size(thissample,1);
N = 100;
if thissample_size < N
    error('Unable to pick %d random rows: the input matrix only has %d rows',N,thissample_size);
end
for sampSets = 1:100
    csvwrite(['randSamp' num2str(sampSets) '.csv'],thissample(randperm(thissample_size,N),:));
end