ggplot: Manually drawing legend, instead of automatic re-sizing of plot sizes

Question

I want to draw a plot, where I can decide what the sizes of the plots are in the legend section. So far, this is what I have for the code:

library(ggplots2)

overlap <- read.delim("/R_plots/num_ins_vs_overlap.txt", sep="\t", row.names=1, header=TRUE)

tools <- overlap$tools
window <- overlap$window
numVars <- overlap$number_of_variants
olPcnt <- overlap$pcnt_overlap
shape <- overlap$shape

s <- qplot(numVars, olPcnt, data=overlap, colour=tools, size=window, shape=shape)

s + scale_shape(solid=FALSE) + labs(title="Number of Variants Detected vs. % Overlap", x="Number of Variants Detected", y="% Overlap")

The data itself, looks like shown here:

        tools   window  number_of_variants      pcnt_overlap    shape
1       scalpel 5       184458  38.32   circle
2       pindel  5       320770  32.42   circle
3       samtools        5       313147  34.16   circle
4       UnifiedGenotyper        5       234746  36.98   circle
5       scalpel 20      184458  39.33   circle
6       pindel  20      320770  33.10   circle
7       samtools        20      313147  35.18   circle
8       UnifiedGenotyper        20      234746  38.38   circle
9       scalpel 50      184458  39.83   circle
10      pindel  50      320770  32.92   circle
11      samtools        50      313147  35.91   circle
12      UnifiedGenotyper        50      234746  39.16   circle
13      scalpel 100     184458  40.34   circle
14      pindel  100     320770  32.74   circle
15      samtools        100     313147  37.49   circle
16      UnifiedGenotyper        100     234746  48.66   circle

The window field has 4 different values: (5, 20, 50 and 100) and I would like these to be the sizes of the plots...and it seems like I got that part right, based on what I see on the plots. The trouble is on the legend, I see sizes of (25, 50, 75 and 100. Is there a way for me to tell the script not to change the sizes this way on the legend, and show the actual sizes of the plots instead?

Thanks in advance,

Young

Answer 1

Try making window a factor:

s <- qplot(numVars, olPcnt, data=overlap, 
           colour=tools, 
           size=as.factor(window), shape=shape)