Dear all, Still I want to filter genes by names. Because exprSet and matrix are numerical, therefore I added rownames value to the matrix like follows: ma.paq is my MAList. my_matrix<-as.matrix.MAlist(ma.paq) row.names(my_matrix)<-ma.paq$genes$Names then I have a matrix with genename as rowname. But I am not quite sure that these genenames and matrix values are still corresponding to eachother as before. I want to know is there any switch during the convertion. or is this mehod doable Thanks, Yanju