arff files is a csv file with headers. Open the arff file with a text editor and remove lines with @ sign, of course as any comment line with %sign. You can also export arff file with weka directly to csv. There are also some online tools easy to use.
Its easy in weka. Just open the arff file in weka GUI than click on save and save as .csv. The csv file is easily readable in Matlab an you can male .mat there.
I have a question about running feature selection algorithms of weka in matlab
does Any body know how i can change the option of a feature selection algorithm of weka in matlab? for example i want to decrease the criteria of error to select more features.