issue regarding understanding of code

[shikhagoel003]

hello sir,
in your code sample.m i could not particulartly understand the use of lines below and the graphs i am obtaining. i am making the code run for 3 classes. my data is 90X9 matrix where first column is label. please explain what are the changes in code i need to make to make it run for my database.
% Make the run index for each observation
k=1;
for i=1:90
if i<= 50
run(i)=i;
elseif k<=50
run(i)=k;
k=k+1;
else
k=1;
run(i)=k;
end
end