[R] multiple plots in the same graph

I'd like to plot y vs x according to the third variable group which has three levels. I am wondering how can I put the three plots in one graph? Thank you (http://groups.yahoo.com)

[R] Variance of Y_hat in a linear model

Y X Z 42.07.0 33.0 33.04.0 41.0 75.0 16.07.0 28.03.0 49.0 91.0 21.05.0 55.08.0 31.0 data-read.table(d.txt,header=TRUE) mod-lm(data$Y~data$X+data$Z) predict(mod) 123456

[R] Predicted value at a new level in lm

Y X Z 42.07.0 33.0 33.04.0 41.0 75.0 16.07.0 28.03.0 49.0 91.0 21.05.0 55.08.0 31.0 data-read.table(d.txt,header=TRUE) mod-lm(data$Y~data$X+data$Z) --- I would like to know the predict value

[R] Variance of fitted value in lm

Hi, I am wondering if a linear model lm(y~ x1+x2) calculates the variance of a fitted value. Thank you Li __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide