Hi
> > > score<-read.csv("http://users.stat.umn.edu/~chen2285/hw/ACT.csv") > score<-read.csv("http://users.stat.umn.edu/~chen2285/hw/ACT.csv") Error in file(file, "rt") : cannot open the connection In addition: Warning message: In file(file, "rt") : unable to connect to 'users.stat.umn.edu' on port 80. > Unable to read data. > > > interaction.plot(sex,rep(1,861),score,fun=mean,legend=F,main="profile of > > sex") > Error: tapply(response, list(x.factor, trace.factor), fun) : > arguments must have same length However you are not telling us whole story. score shall be data frame and length(data.frame) results in number of columns. >From help page x.factor a factor whose levels will form the x axis. trace.factor another factor whose levels will form the traces. response a numeric variable giving the response your second variable to interaction plot is numeric - shall be factor your third variable is probably data frame, shall be numeric. It is advisable to give to functions values they expect. Some functions can crunch unexpected data but the results can be misleading if not wrong. Regards Petr > > > length(sex) > [1] 861 > > length(type) > [1] 861 > > length(score) > [1] 3 > > How can I alter the length of the variable score here to make this function > work? > or any other way to perform interaction plot? > > > -- > View this message in context: http://r.789695.n4.nabble.com/arguments- > must-have-same-length-tp4625885.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. ______________________________________________ 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.