Hi all, I must correct what I have written: 'Label' works like a charm in demo8classification.m, but I have trouble when I try to use a flowchart design. So basically I want to start this way: myflow.tmp.a = miraudio ('Design', 'Extract', -25, +25, 'Middle', 'Sampling', 44100, 'Label', 1:3); and finish this way: output = mireval (myflow, 'Folders'); mirexport ('export.arff', output); But I get this error: ??? Error using ==> fprintf Invalid file identifier. Use fopen to generate a valid file identifier. Error in ==> mirexport>ARFFformat at 313 fprintf(fid,'@RELATION %s\n\n',title); Error in ==> mirexport at 94 ARFFformat(stored,f,title,class,classes,add); Maybe someone can give me a hand with this? Greetings, Martin