On 02/08/2014 02:54 AM, Douglas M. Hultstrand wrote:
Hello,
I am trying to generate a plot legend that contains calculated summary
statistics, one statistic is R^2. I have tried several variations using
the commands "expression" and "bqoute" as stated on the R help pages. I
have not been able to get the R^2 super script correct along with the
calculated statistics.
I provided an example below, what I want is the legend (wdt_leg and
spas_leg) as below but with the R^2 as superscript.
# Example Data
x=c(1,2,3,4); y=c(1,2,3,4); z=c(1.25,1.5,2.5,3.5)
# first stats based on data, used to populate legend
wdt_n = 50; wdt_mbias = 0.58
wdt_mae = 2.1; wdt_R2 = 0.85
# second stats based on data, used to populate legend
spas_n = 50; spas_mbias = 0.58
spas_mae = 2.1; spas_R2 = 0.85
# create legend
wdt_leg<- paste("WDT (N = ", wdt_n,", Bias = ",wdt_mbias,", MAE =
",wdt_mae, ", R2 = ", wdt_R2, ")", sep="")
spas_leg<- paste("SPAS (N = ", spas_n,", Bias = ",spas_mbias,", MAE =
",spas_mae, ", R2 = ", spas_R2, ")", sep="")
# create plot
plot(x,y, col="red1", pch=1); lines(x,z, type="p", col="green4",pch=3)
leg.txt<- c(spas_leg, wdt_leg)
legend("topleft", legend = leg.txt, col=c("red1","green4"), pch=c(1,3),
cex=0.85)
Hi Doug,
I set out to get your legend strings turned into expressions and after
several tries, gave up. Getting superscripts and subscripts in base
graphics is fairly easy:
supsubtext<-function(x,y,label,sup=NA,sub=NA,xadj=0.5,...) {
nlabchar<-nchar(label)
yadj<-rep(0.5,nlabchar)
if(!is.na(sup)) yadj[sup]<-0
if(!is.na(sub)) yadj[sub]<-1
labbits<-strsplit(label,"")[[1]]
currentx<-x
for(labchar in 1:nlabchar) {
text(x,y,labbits[labchar],adj=c(xadj,yadj[labchar]),...)
x<-x+strwidth(labbits[labchar])
}
}
The above function will display a line of text in which any character
the index of which is in "sup" will be superscripted and any in "sub"
will be subscripted. It is possible to add "cex" values to reduce the
size of those characters if necessary. You can then construct a
serviceable legend manually like this:
plot(x,y, col="red1", pch=1); lines(x,z, type="p", col="green4",pch=3)
points(c(1,1),c(3.9,3.7),pch=c(1,3),col=c("red1","green4"))
wdt_leg<-"WDT (N = 50, Bias = 0.58, MAE = 2.1, R2 = 0.85)"
spas_leg<-"SPAS (N = 50, Bias = 0.58, MAE = 2.1, R2 = 0.85)"
supsubtext(1.2,3.9,spas_leg,sup=40)
supsubtext(1.2,3.7,wdt_leg,sup=40)
xylim<-par("usr")
segments(c(xylim[1],3.4),c(3.5,3.5),c(3.4,3.4),c(3.5,xylim[4]))
I am sure that someone more expert with expressions will post a more
elegant solution.
Jim
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