CODEWITHSUNDEEP
rplot
Robert Dodier
Robert Dodier

Reputation: 17585

How to draw lines with lines() without preceding call to plot() in R

Given these data:

> x <- c(1, 2)
> y1 <- c(4, 3)
> y2 <- c(3, 6)

I'd like to draw lines for (x, y1) and (x, y2) in different colors on the same plotting frame. This has the desired effect:

> plot (x, y1, type='l', col='red')
> lines (x, y2, col='green')

Is there a way to do that using lines for both lines? This creates just an empty plot:

> plot.new ()
> lines (x, y1, col='red')
> lines (x, y2, col='green')

I guess plot is calling some function to get the plot started before drawing the first line; it doesn't appear to be plot.new. What is that function? Can I call it myself before calling lines?

EDIT: I am working with R 3.0.2 on Ubuntu 14.04.

Upvotes: 3

Views: 3491

Answers (3)

Colonel Beauvel
Colonel Beauvel

Reputation: 31181

For plot solution, you need to create a plot with some data and mask those data with n option (I also employed ann=F to mask x and y labels):

plot(x, y1, type='n', ann=F, xlim=c(1,2),ylim=c(1,6))
lines (x, y2, col='green')
lines (x, y1, col='red')

enter image description here

Upvotes: 3

IRTFM
IRTFM

Reputation: 263451

 x <- c(1, 2)
 y1 <- c(4, 3)
 y2 <- c(3, 6)
 plot.new(); plot.window(xlim=c(1,2),ylim=c(1,6) )
 lines (x, y1, col='red')
 lines (x, y2, col='green')

enter image description here

I'm getting a nattering message about explaining my code but I do think Robert is smart enough to figure this out. Following the links on the ?plot.window page lets you see other low-level functions like ?xy.coords. You can see the code for plot.default by typing its name at a console prompt. In that code you see a new function defined but it is really just gathering some parameters before calling plot.window:

localWindow <- function(..., col, bg, pch, cex, lty, lwd) plot.window(...)
# which gets called later in the code.

Upvotes: 6

CJGodfrey
CJGodfrey

Reputation: 476

In the plot() command, use type="n" to set up the plot invisibly. Then add your line segments with successive lines().

Upvotes: 2

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