[R] Trendline for a subset of data

Greg Snow Greg.Snow at imail.org
Mon Oct 12 20:57:35 CEST 2009

Others have show how to use the segments function, but this can also be done using the original abline function along with the clip function.  Here is an example:

plot( iris$Petal.Width, iris$Petal.Length, 

tmp <- levels(iris$Species)
tmp2 <- par('usr')

for(i in 1:3) {
	fit <- lm( Petal.Length ~ Petal.Width, data=iris, subset= Species==tmp[i] )
	tmpx <- with(iris, Petal.Width[ Species==tmp[i] ] )
	clip( min(tmpx), max(tmpx), tmp2[3], tmp2[4] )
	abline( fit, col=c('red','green','blue')[i] )

Hope this helps,

Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Steve Murray
> Sent: Friday, October 09, 2009 3:51 AM
> To: r-help at r-project.org
> Subject: [R] Trendline for a subset of data
> Dear all,
> I am using abline(lm ...) to insert a linear trendline through a
> portion of my data (e.g. dataset[,36:45]). However, I am finding that
> whilst the trendline is correctly displayed and representative of the
> data portion I've chosen, the line continues to run beyond this data
> segment and continues until it intersects the vertical axes at each
> side of the plot.
> How do I display the line so that it only runs between point 36 and 45
> (as shown in the example above) as doesn't continue to display a line
> throughout the rest of the plot space?
> Many thanks,
> Steve
> _________________________________________________________________
> View your other email accounts from your Hotmail inbox. Add them now.
> http://clk.atdmt.com/UKM/go/167688463/direct/01/
> ______________________________________________
> R-help at 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.

More information about the R-help mailing list