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GGPLOT2: Distance of discrete values of from each end of x-axis

Submitted by Tom on February 4, 2012

I have been working with the code below. Everything seems to work
okay, except that the discrete values on the x-axis are far from each
end of the graph. I've tried several things including changing the
discrete values and playing with the limits, but can't get it to work.
I tested this on simulated data and do not have the same problem, so I
guessing it is how I'm processing the data. I'd appreciate any
pointers on how to adjust this and/or process the data correctly so it
does not occur. The data file being imported is a combination of
continuous, discrete and string variables.

The data I use:

id_finger   sex pre_post    angle
1   F   0   7
1   F   2   5
2   F   0   11
2   F   2   1
3   F   0   21
3   F   2   7
4   M   0   12
4   M   2   1
5   F   0   11
5   F   2   4
6   M   0   18
6   M   2   8
7   M   0   28
7   M   2   9
8   F   0   10
8   F   2   2
9   M   0   12
9   M   2   5
10  F   0   14
10  F   2   0
11  M   0   27
11  M   2   5
12  M   0   15
12  M   2   3
13  F   0   19
13  F   2   0
14  M   0   5
14  M   2   4
15  M   0   24

And my code:

vicryl.wide <- read.table("C:/vicryl2.csv",
                     header=TRUE, sep=",", na.strings=" ")
 
library(reshape2)
vicryl.long <- melt(vicryl.wide,
               id.vars=c("id_finger","sex"),
               measure.vars=c("pre_angle_r", "post_angle_r"),
               variable.name="pre_post")
 
names(vicryl.long)[names(vicryl.long)=="value"] <- "angle"
 
levels(vicryl.long$pre_post)[levels(vicryl.long$pre_post)=="pre_angle_r"] <- 0
levels(vicryl.long$pre_post)[levels(vicryl.long$pre_post)=="post_angle_r"] <- 2
 
vicryl.long <- vicryl.long[ order(vicryl.long$id_finger,
vicryl.long$pre_post), ]
 
library(ggplot2)
ggplot(data=vicryl.long, aes(x=pre_post, y=angle, group=id_finger)) +
geom_line()