How can I adjust the legend box? - r

Question

This is my code:
score <- tapply(exams$writing.score
, list(exams$gender,
exams$race.ethnicity
)
, mean)
plot1 <- barplot(score
, beside = TRUE
, main = "Comparison of Writing Score"
, col = c("red", "lightyellow")
, xlab = "Race Ethnicity Group"
, ylab = "Average Writing Score"
, legend.text = c("Female", "Male")
, args.legend = list(x = "topright")
)
As I want to make the box: Female and Male smaller so it does not hide the bar behind. How can I make the legend box smaller? I tried to move it to the top right of the chart, but I do not think it moves.

Answer 1

You could use the argument cex. Here is a reproducible example:
data <- matrix(c(1,2,3,4,5,6,7,8,9,10), ncol = 5)
colnames(data) <- paste0("V", 1:5)
rownames(data) <- c('A','B')
# Normal
barplot(data, col = 1:nrow(data))
legend("topright", legend = rownames(data), pch = 15, col = 1:nrow(data))
# With cex
barplot(data, col = 1:nrow(data))
legend("topright", legend = rownames(data), pch = 15, col = 1:nrow(data), cex = 0.5)
Created on 2022-10-21 with reprex v2.0.2

Answer 2

Another option (in addition to using cex as #Quinten shows) is to also change the inset to move the legend outside of the plot boundary, as well as using par to specify the parameters for margins, etc.
par(mar = c(5, 4, 4, 8),
xpd = TRUE)
# Normal
barplot(df, col = 1:nrow(df))
legend(
"topright",
inset = c(-0.1, 0),
# Create legend outside of plot
legend = rownames(df),
pch = 15,
col = 1:nrow(df),
cex = 0.8
)
Data
df <- structure(c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), dim = c(2L, 5L), dimnames = list(
c("Female", "Male"), c("V1", "V2", "V3", "V4", "V5")))

Answer 3

It doesn't move because you already are at the very top. To move the top upwards and let the legend follow, expand ylim.
Also try if you like setting the legend horizontal and remove the bty (boxtype). Don't choose the cex too small.
barplot(score
, beside=TRUE
, main="Comparison of Writing Score"
, col=c("red", "lightyellow")
, xlab="Race Ethnicity Group"
, ylab="Average Writing Score"
, legend.text=c("Female", "Male")
, args.legend=list(x="topright", cex=.9, horiz=TRUE, bty='n')
, ylim=c(0, max(score)*1.2)
)
Data:
score <- structure(c(96.8, 95.2, 100, 100, 89.7, 89.2, 81.4, 81, 85.1,
82), dim = c(2L, 5L), dimnames = list(c("1", "2"), c("A", "B",
"C", "D", "E")))