Question

I’m trying to create a pretty simple scatter plot with two data series. I would like to specify the color of each point through a fourth column in the dataframe I’m using. I’ve got the scatter plot itself close to where I want it, with two different glyphs for the two series, but the colors are not being assigned to the right points. I’m pretty new to R so I’m not sure where to go from here. Any help would be appreciated. Sample data and code attached (can’t upload images yet).

Sample Data:

x   y   group   color
0   0   g   red
2   -1  g   blueviolet
0   -1  g   brown
2   -2  g   blueviolet
0   -11 g   blue
2   -6  g   blue
0   1   g   coral
0   -2  g   blue
2   -1  h   blueviolet
0   -1  h   brown
2   -2  h   blueviolet
0   -11 h   blue
2   -6  h   blue
0   1   h   coral
2   -8  h   blue
4   -2  h   coral
1   -5  h   brown
1   -9  h   violet
-2  2   h   blue

Sample R code:

ztest=read.table(file="ztest.txt",sep="\t",header=TRUE)
plot(ztest$x,ztest$y,type='n')
points(ztest[ztest$group=="g",]$x,ztest[ztest$group=="g",]$y,col=ztest$color,pch=3,cex=.75)
points(ztest[ztest$group=="h",]$x,ztest[ztest$group=="h",]$y,col=ztest$color,pch=1,cex=1.75)

Answer 1

You seem to be subsetting the points, but not subsetting the colours. Instead of

points(ztest[ztest$group=="g",]$x,ztest[ztest$group=="g",]$y,col=ztest$color, ...

try

points(ztest[ztest$group=="g",]$x,ztest[ztest$group=="g",]$y,col=as.character(ztest[ztest$group=="g",]$color), ....

Hope this helps