Here's an example:
x <- runif(100)
sex <- sample(0:1, 100, replace = TRUE)
y <- sex + 2*x + x*sex + rnorm(100)
dfr <- data.frame(y, x, sex)
f1 <- lm(y ~ x, data = dfr, subset = sex == 0)
f2 <- lm(y ~ x, data = dfr, subset = sex == 1)
plot(x, y, pch = sex+1)
abline(f1, col = 2, lty = 2)
abline(f2, col = 3, lty = 3)
legend('topleft', c('male', 'female'), lty = 2:3, col =
2:3)
For some fancier plots see the ggplot2 examples here:
http://had.co.nz/ggplot2/stat_smooth.html
hth,
Kingsford Jones
On Tue, Oct 20, 2009 at 1:20 PM, Marsha Melnyk <mmelnyk at stevens.edu>
wrote:> I am trying to make a scatterplot with containing three columns. ?I
> know how to plot the two columns but now the third column consists of M
> or F (male or female) and I don't know how to separate the data so I
> can make two separate regression lines on the same graph.
>
> meta ? #name of file
> plot(meta$mass, meta$rate, xlab="mass", ylab="rate")
>
> I can make the regression line with all the data but I just don't know
> how to split everything up.
>
> abline(lm(rate ~ mass, data=meta), col="red")
>
>
>
> Thanks,
> Marsha
>
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