# [R] Getting discrete colors on plot

PIKAL Petr petr.pikal at precheza.cz
Fri Jan 18 08:09:30 CET 2013

```Hi

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Mary
> Sent: Thursday, January 17, 2013 6:02 PM
> To: r-help at r-project.org
> Subject: Re: [R] Getting discrete colors on plot
>
> Hi,
>
> This is my first post; I'm new to R but am a senior statistical
> programmer.  I have done a lot of graphs using SAS Graph but now am
> trying to transition to using graphs in R.
>
> I'm trying to produce a graph where the colors have three categories-
> ideally I would like them to be Green for good, Yellow for
> Questionable, and Red for bad.
>
> So I tried to do this in GGPLOT; here is my code:
>
> id <-       c(1,2,3,4,5)
> x1 <-       c(5,2,3,5,1)
> x2 <-       c(4,1,3,5,1)
> x3 <-       c(5,2,3,5,1)
> x4 <-       c(4,3,3,5,1)
> x5 <-       c(3,1,3,5,1)
> colorvar <- c(3,1,2,3,1)
>
> mydata <- data.frame(id,x1,x2,x3,x4,x5,colorvar)
>
> # convert to long format
> require("reshape")
> mydata_long <- melt(mydata, id=c("id", "colorvar"))
>
> require("ggplot2")
> p <- ggplot(data=mydata_long,
>        aes(x=variable, y=value,
> group=id, colour = colorvar)) +
>     geom_line()
> p
>
>
> This works, but I get more colors on the graph than my colorvar has.  I
> have 3 colors on my colorvar, but 5 colors show up on the graph,
> including 1.5 and 2.5.   How do I tell ggplot only to use the 3 colors
> and not give me a gradient of colors?  Also how would I specify the
> colors that I want, such as the RGB equivalents of green, yellow, and
> red?  My real data will have many more records.

Learn to use factors.

str(mydata)
'data.frame':   5 obs. of  7 variables:
\$ id      : num  1 2 3 4 5
\$ x1      : num  5 2 3 5 1
\$ x2      : num  4 1 3 5 1
\$ x3      : num  5 2 3 5 1
\$ x4      : num  4 3 3 5 1
\$ x5      : num  3 1 3 5 1
\$ colorvar: num  3 1 2 3 1
>

Your colorvar is numeric therefore the scale. If you want to make it discrete change it to factor.

mydata_long\$colorvar<-factor(mydata_long\$colorvar)

and use your function to see the difference.

Regards
Petr

>
> -Mary
>
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