[R] How to change min and max of plot axis

[Duncan Murdoch]

On 21/06/2008 11:25 AM, Luis Orlindo Tedeschi wrote:
> All; this might be an easy question but I cannot make it work. I would
> like to set the min and max of the y axis of a plot. I know I have to
> use par("usr"), but after I do the plot() the axis values get changed.
> 
> x<-rnorm(20)
> Y<-x+rnorm(20,0,.1)
> plot(y,x)
> par("usr")
> 
> # let's say I have -2.8 1.15 -2.8 1.16 for par("usr")
> # let's say I need to change the Y-axis to be -5 to 5
> 
> usr<-par("usr")
> par(usr=c(usr[1:2],-5,5))
> plot(y,x)
> 
> # it does not take the -5 to 5???
> 
> Is there any way to set the axis values?

plot() will set up the coordinate system.  You can use the ylim argument 
to set the limits, e.g.

plot(y, x, ylim=c(-5,5))

(This is a little confusing, since the y variable ends up on the x axis 
and vice versa:  the convention in R is plot(x, y).)

Duncan Murdoch