Hi,all! after executing : library(Matrix) spr_mat<-sparseMatrix(mydataframe$r,mydataframe$c,x=mydataframe$v) diagr<- diag(vr,nrow=ins_num) A<-diagr%*%spr_mat I encountered a error "not-yet-implemented method for <list> %*% <dgCMatrix>" could someone show me some tips? many hanks! best regards! June ---------------- Zhu Man, (TEL)13851764837 School of Computer Science & Engineering Southeast University, Nanjing [[alternative HTML version deleted]]