Plot 3 categories of dots with single x axis scale - R ggplot2

Question

I want to visualize how does the length of a sequence affect numbers of errors in different categories.

The problem actually starts from the file formatting, but having a file formatted as follows:

category count length
s 12 1500
i 13 1500
d 15 1500
s 17 1600
i 18 1600
d 22 1600
s 14 1500
i 15 1500
d 17 1500
s 30 1800
i 40 1800
d 0 1800

How can I plot this to have length column as x-axis, s,i,d as dots of different colours or shapes.

Answer 1

I'm not sure why you accepted the above answer because you've asked specificly for ggplot2. So I'm adding the ggplot solution just in case

library(ggplot2)
test <- data.frame(category = factor(c("s","i","d","s","i","d","s","i","d","s","i","d")),
                   count = c(12,13,15,17,18,22,14,15,17,30,40,0),
                   length = c(1500,1500,1500,1600,1600,1600,1500,1500,1500,1800,1800,1800))

ggplot(test, aes(x = length, y = count)) + geom_point(aes(colour = category))

Answer 2

Perhaps this works:

xx = read.table("/tmp/tmp.txt", sep=" ", header=TRUE)
yy = split(xx[c("count", "length")], xx[["category"]])
with(yy[["d"]],
     plot(y=count, x=length,
          xlim=c(min(xx[["length"]]), max(xx[["length"]])),
          ylim=c(min(xx[["count"]]), max(xx[["count"]])),
          col="red"))
with(yy[["i"]], points(y=count, x=length, col="blue"))
with(yy[["s"]], points(y=count, x=length, col="green"))