I tried your instructions, as shown. > library(chron) > library(zoo) > z1<-read.zoo("test1.csv",header=TRUE,sep=",",FUN=times) > z2<-read.zoo("test2.csv",header=TRUE,sep=",",FUN=times) > z12<-merge(z1,z2) > z3<-na.approx(z12,xout=time(z1)) Error in approx(along[!na], y[!na], along[na], ...) : invalid interpolation method In addition: Warning message: the condition has length > 1 and only the first element will be used in: if (is.na(method)) stop("invalid interpolation method") > source("http://r-forge.r-project.org/plugins/scmsvn/viewcvs.php/*checkout*/pkg/zoo/R/na.approx.R?rev=676&root=zoo") > z3<-na.approx(z12,xout=time(z1)) > z3 z1 z2 01:01:30 0.34860813 0.21977817 01:02:00 0.61306418 0.46662656 01:02:30 0.01495898 0.75482666 01:03:00 0.27035612 0.73832408 ...
It looks that the data of z3 shows only values corresponding to times in z1. In the previous merge, z3 consisted of values for times in both z1 and z2, e.g.: z1[, 2] z2[, 2] 01:01:01 0.54186455 0.17558467 01:01:30 0.34860813 0.20682491 01:01:42 0.48083615 0.23806514 01:02:00 0.61306418 0.49837120 With respect to advice about seeking help, I think it would be very good if your comments about using the command 'textConnection()' were added to the FAQ section or the posting guide, to help novices improve the quality of asking for help. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.