Further to my recent post on this topic and thanks to help received already
(thanks BTW), I've got back-to-back plots working nicely to give me population
pyramids, with some overlaid point data from a different time period, using the
code below.
#packages
library(ggplot2)
library(reshape2)
library(plyr)
#sample data
set.seed(33)
df<-data.frame(ag=c(1:18),males_year1=sample(100:200,18),females_year1=sample(100:200,18),males_year2=sample(100:200,18),females_year2=sample(100:200,18))
#melt the data set
df<-data.frame(melt(df,id="ag"))
df
#here is the plot
p<-ggplot(df)+
geom_bar(subset=.(df$variable=="males_year1"),stat="identity",aes(x=ag,y=value),fill="#6666FF")+
geom_bar(subset=.(df$variable=="females_year1"),stat="identity",aes(x=ag,y=-value),fill="#FF9333")+
geom_point(subset=.(df$variable=="males_year2"),stat="identity",aes(x=ag,y=value),size=3,colour="#330099")+
geom_point(subset=.(df$variable=="females_year2"),stat="identity",aes(x=ag,y=-value),size=3,colour="#CC3300")+
coord_flip()+
theme_bw()+
scale_y_continuous(limits=c(-200,200),breaks=seq(-200,200,50),labels=abs(seq(-200,200,50)))+
scale_x_continuous(limits=c(0,19),breaks=seq(1,18,1),labels=abs(seq(1,18,1)))+
xlab("age group")+ylab("population")+
theme_bw()+
xlab("age group")+
ylab("population")+
geom_text(y=-100,x=19.2,label="Females")+
geom_text(y=100,x=19.2,label="Males")
p
Two questions remaining. Firstly have I used a large amount of code to acheive
this or is this about right for the effect that I'm after?
Secondly I'm quite confused about how to put a legend onto a plot like this.
I'm getting slowly into the ggplot way of doing things, but I'm totally baffled
by legends; say I wanted a legend with an appropriate label for both genders
and both time periods showing the colours of the bars and dots I've used here
as examples, how do I do this? I've tried scale_fill with a bunch of arguments
to no avial. I'm confused about where in the hierarchy of ggplot commands you
actually build the legend and how you map it to your data. The usual trawl of
the package pdf / cook book for R etc hasn't really helped. Can someone show me
how to do this please?
Many thanks.
Gavin.
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