<HTML><BODY STYLE="font:10pt verdana; border:none;"><DIV>Hi,</DIV> <DIV>I have a matrix and time series "xmat". I have no problem executing any matrix functions except t(xmat) which gives the following error message. My question if "xmat" is a matrix why I can not execute this matrix function?? converting the time series and matrix into a data frame solves the problem</DIV> <DIV>>dim(xmat)</DIV> <DIV>[1] 98 7<BR>> t(xmat)<BR>Error in "tsp<-"(*tmp*, value = xtsp) : invalid time series parameters specified<BR>> is.matrix(xmat)<BR>[1] TRUE<BR>> is.ts(xmat)<BR>[1] TRUE<BR>> is.data.frame(xmat)<BR>[1] FALSE<BR><BR>Ahmad Abu Hammour<BR></DIV></BODY></HTML>