Dear R-users,
This is a follow-up on a quite old post of mine which dealt with margins
in the pairs function. I thought my problem was solved, but it doesn't
seem so (see the code below).
I use the pairs function to produce matrix plots, where distinct groups
are represented by dots of different colors within each panel. My
troubles start when I add a legend at the bottom of the plot. The steps are:
1- I build my dataframe
2- I plot the graph and define the margins within pairs with oma (I want
to add 5 + my number of group lines at the bottom)
3- I use gridBase functions to add the legend (symbol + text)
The result is an overlay of the legend on the plot. It looks like the
lines do not have the same size when using pairs or the gridBase
functions. Could anyone explain this discrepancy to me?
Thank you in advance for your help.
Sebastien
####### START########
library(gridBase)
my.Group.number=12
my.df<-data.frame(rnorm(my.Group.number*20, mean=5,
sd=2),rnorm(my.Group.number*20, mean=4,
sd=1.6),rnorm(my.Group.number*20, mean=8,
sd=3),rnorm(my.Group.number*20, mean=6,
sd=1),rep(letters[1:my.Group.number],each=20))
names(my.df)<-c("Var1","Var2","Var2","Var2","Group")
pairs(my.df[1:4],
main = "My Title",
pch = 21,
col =rainbow(n=my.Group.number)[unclass(my.df$Group)],
bg = rainbow(n=my.Group.number)[unclass(my.df$Group)],
oma = c(5 + my.Group.number, 3, 5, 3)
)
mylegend = paste("Group ",letters[1:my.Group.number],sep="")
mylegend.width = strwidth(mylegend[which.max(nchar(mylegend))],
"figure", mylegend.Cex(mylegend,myTarget = 0.90))
vps <- baseViewports()
pushViewport(vps$inner)
for (j in 1:my.Group.number) {
grid.text(mylegend[j],
x = unit((1-mylegend.width)/2,"npc"),
y = unit(1 + my.Group.number - j,"lines"),
gp = gpar(cex = 1),
just = "left",
draw=TRUE)
grid.points(x =
unit((1-mylegend.width)/2,"npc")-convertUnit(unit(0.5,"lines"),"npc"),
y = unit(1 + my.Group.number - j,"lines"),
size = unit(0.5, "lines"),
default.units = "lines",
pch = 21,
gp = gpar(col = rainbow(n=my.Group.number)[j],fill =
rainbow(n=my.Group.number)[j]),
draw=TRUE)
}
######## END ########
Prof Brian Ripley a écrit :
On Tue, 28 Aug 2007, Sébastien wrote:
Thanks you very much.
I did not thought about calling oma inside the pairs function...
Do you know by any chance why 'pairs' behaves differently from
'plot', with regards to the plot dimension ?
Well, it is an array of figures so why should it be the same? See
chapter 12 of 'An Introduction to R'.
Prof Brian Ripley a écrit :
From ?pairs
The graphical parameter 'oma' will be set by 'pairs.default'
unless supplied as an argument.
so try
pairs(iris[1:4], main = "Anderson's Iris Data -- 3 species", pch = 21,
bg = c("red", "green3", "blue")[unclass(iris$Species)],
oma = c(8,3,5,3))
On Tue, 28 Aug 2007, Sébastien wrote:
Dear R-users,
I would like to add a legend at the bottom of pairs plots (it's my
first
use of this function). With the plot function, I usually add some
additional space at the bottom when I define the size of the graphical
device (using mar); grid functions then allows me to draw my legend
as I
want.
Unfortunatley, this technique does not seem to work with the pairs
function as the generated plots use all the available space on the
device (see below). I guess I am missing a key argument... my attempts
to modify the oma, mar, usr arguments were unsuccesfull, and I
could not
find any helpful threads on the archives.
As usual, any advice would be greatly appreciated
Sebastien
pdf(file="C:/test.pdf", width=6, height= 6 + 0.2*6)
par(mar=c(5 + 6,4,4,2)+0.1)
pairs(iris[1:4], main = "Anderson's Iris Data -- 3 species", pch = 21,
bg = c("red", "green3", "blue")[unclass(iris$Species)])
dev.off()
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