Hello, Is this intended: > m <- data.frame( date = seq.Date( as.Date("2000-01-01"), as.Date("2000-01-05"), by = "day" ) ) > sapply( m, typeof ) date "double" > as.matrix( m ) date [1,] "2000-01-01" [2,] "2000-01-02" [3,] "2000-01-03" [4,] "2000-01-04" [5,] "2000-01-05" > typeof( as.matrix( m ) ) [1] "character" In particular : > m <- data.frame( date = seq.Date( as.Date("2000-01-01"), by = "day", length.out = 50 ), x = rnorm(50) ) > loess( x ~ date, data= m) Error: NA/NaN/Inf in foreign function call (arg 2) In addition: Warning message: NAs introduced by coercion > loess( x ~ as.double(date), data= m) Call: loess(formula = x ~ as.double(date), data = m) Number of Observations: 50 Equivalent Number of Parameters: 4.42 Residual Standard Error: 0.9712 Replacing this line in loess : x <- as.matrix(x) by this : x <- tryCatch( do.call( cbind, lapply( x, as.double ) ), error = function(e){ stop( "predictors must all be numeric" ) } ) does the trick for me. Romain -- Romain Francois Professional R Enthusiast +33(0) 6 28 91 30 30 http://romainfrancois.blog.free.fr |- http://tr.im/BcPw : celebrating R commit #50000 |- http://tr.im/ztCu : RGG #158:161: examples of package IDPmisc `- http://tr.im/yw8E : New R package : sos