Sampling data in MATLAB

Question

I have two pieces of data. One is the actual fulldata which is a dataset of 49625x6 numeric data, and the other is the index of that data with the target_class

Answer 1

Extract the 'normal' records using strmatch:

normIdx = strmatch('normal.', Book2);
normalSubset = fulldata(normIdx, :);

Then to generate a list of 250 random non repeating integers I googled "matlab list of non repeated random integers" and from the first result:

p = randperm(size(normalSubset , 1));
p = p(1:250)-1;

So now to get your 250 randomly selected normal records

normalSample = normalSubset (p, :);

normalSample will be 250 x 6. now do the same with 'not normal.' to get a notNormalSample (750 x 6) and then combine then to get

sample = [normalSample ; notNormalSample ]

So in sample all the normals will appear before the not normals, if you want to mix them up use randperm() again:

sample = sample(randperm(1000), :);