ggplot2:scatterplots for all possible combinations of variables - r

Question

I want to plot graphs for all possible combinations of variables. My code is below:
set.seed(12345)
a <- data.frame(Glabel=LETTERS[1:7], A=rnorm(7, mean = 0, sd = 1), B=rnorm(7, mean = 0, sd = 1), C=rnorm(7, mean = 0, sd = 1))
T <- data.frame(Tlabel=LETTERS[11:20], A=rnorm(10, mean = 0, sd = 1), B=rnorm(10, mean = 0, sd = 1), C=rnorm(10, mean = 0, sd = 1))
library(ggplot2)
for(i in 2:(ncol(a)-1))
{
for(j in (i+1):ncol(a))
{
r <- 0.08
p <- ggplot(data=a, mapping=aes(x=a[, i], y=a[, j])) + geom_point() + theme_bw()
p <- p + geom_text(data=a, mapping=aes(x=a[, i], y=a[, j], label=Glabel),
size=3, vjust=1.35, colour="black")
p <- p + geom_segment(data = T, aes(xend = T[ ,i], yend=T[ ,j]),
x=0, y=0, colour="black",
arrow=arrow(angle=25, length=unit(0.25, "cm")))
p <- p + geom_text(data=T, aes(x=T[ ,i], y=T[ ,j], label=Tlabel), size=3, vjust=0, colour="red")
dev.new()
print(p)
}
}
This code works fine. But the method used here is not recommended (See #baptiste comment) and does not work in function. I want to know what is the best and recommended way to accomplish this task. Thanks in advance for your help.

Answer 1

Alright this is garbage but the best I could do. It's super inefficient as it recreates a partial data with each loop through lapply. Maybe someone else has something better:
MAT <- outer(names(df)[-1], names(df)[-1], paste)
combs <- sapply(MAT[lower.tri(MAT)], function(x) strsplit(x, " "))
ind <- lapply(combs, function(x) match(x, names(df)))
plotter <- function(cn) { #start junky function
NAMES <- colnames(df)[cn]
df2 <- df[cn]
names(df2)<- c('x1', 'x2')
p <- ggplot(data=df2, aes(x1, x2)) + geom_point() + theme_bw() +
scale_x_continuous(name=NAMES[1]) +
scale_y_continuous(name=NAMES[2])
dev.new()
print(p)
} #end of junky function
lapply(ind, function(x) plotter(cn=x))
EDIT: This is a bit better:
x <- match(names(df)[-1], names(df))
MAT <- outer(x, x, paste)
combs <- t(sapply(MAT[lower.tri(MAT)], function(x) as.numeric(unlist(strsplit(x, " ")))))
plotter <- function(cn) {
NAMES <- colnames(df)[cn]
df2 <- df[cn]
names(df2)<- c('x1', 'x2')
p <- ggplot(data=df2, aes(x1, x2)) + geom_point() + theme_bw() +
scale_x_continuous(name=NAMES[1]) +
scale_y_continuous(name=NAMES[2])
dev.new()
print(p)
}
apply(combs, 1, function(x) plotter(cn=x))