Along the lines of my comment, you might find the following helpful:
# data generation ---------------------------------------------------------
set.seed(1)
mat <- matrix(runif(4*7, min=0, max=10), 7, 4)
rownames(mat) <- 1:7
colnames(mat) <- LETTERS[1:4]
# plotting settings -------------------------------------------------------
ylim <- range(mat)*c(1,1.5)
angle1 <- rep(c(45,45,135), length.out=7)
angle2 <- rep(c(45,135,135), length.out=7)
density1 <- seq(5,35,length.out=7)
density2 <- seq(5,35,length.out=7)
col <- 1 # rainbow(7)
# plot --------------------------------------------------------------------
op <- par(mar=c(3,3,1,1))
barplot(mat, beside=TRUE, ylim=ylim, col=col, angle=angle1, density=density1)
barplot(mat, add=TRUE, beside=TRUE, ylim=ylim, col=col, angle=angle2, density=density2)
legend("top", legend=1:7, ncol=7, fill=TRUE, col=col, angle=angle1, density=density1)
par(bg="transparent")
legend("top", legend=1:7, ncol=7, fill=TRUE, col=col, angle=angle2, density=density2)
par(op)
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…