How to write a circulation when save selected data into new matrix and then save new matrix into a text file

I have a 140*1 matrix 'res' which consists of integers from 1 to 5.Now I am going to save all row numbers of integer into a new matrix label 1， and all row numbers of integer into a new matrix label 2. I used code below to get the corresponding data. However, if i don't know the length of original matrix 'res', how can i get the data using a circulation.（e.g label 'p'=find(res==p))

nClass = length(unique(res));
label1=find(res==1);
label2=find(res==2);
label3=find(res==3);
label4=find(res==4);
label5=find(res==5);
fid=fopen('1235.txt','wt');
fprintf(fid,'Docum ID: ');
fprintf(fid,'[%d]  ',label1);
fprintf(fid,'\n\n');
fprintf(fid,'Docum ID: ');
fprintf(fid,'[%d]  ',label2);
fprintf(fid,'\n\n');
fprintf(fid,'Docum ID: ');
fprintf(fid,'[%d]  ',label3);
fprintf(fid,'\n\n');
fprintf(fid,'Docum ID: ');
fprintf(fid,'[%d]  ',label4);
fprintf(fid,'\n\n');
fprintf(fid,'Docum ID: ');
fprintf(fid,'[%d]  ',label5);
fprintf(fid,'\n\n');
fclose(fid);

Answer 1

[Stephen23]

The trick is do not create numbered variables:

fid = fopen('12345.txt','wt');
for k = 1:numel(res)
    idx = find(res==k);
    fprintf(fid,'%d  ',idx);
    fprintf(fid,'\n\n');
end
fclose(fid);

Although beginners think that numbered variables are a great idea, they actually just lead beginners to some very bad, slow buggy code:

http://www.mathworks.com/matlabcentral/answers/196952-how-to-create-new-variables-in-batches-with-strcat

[Yunfei Zhang]

Thank you for your reply.I used to think numbered variables can be easier to understand and establish logical links. It seems that numbered variables just make my program more complicated. I will try to avoid that in the future.In addition, I think it's better to use 'wt' instead of 'rt' in this case.