Using R to create brick block graphs
R provides powerful graphics functions. We can use it to draw very complicated and beautiful graphs. Here provides a complete solution to draw brick block graph in R. The function name is brickblock that takes a matrix, graph height, a vector of x-labels, and groupname as inputs. The length of vector should be same as the second dimension of the matrix. The following lists the function code.
brickblock <- function(m, height, xlabs, groupname)
{
mdim <- dim(m); # dimmension of the input matrix
margin <- 30; # default margin
padding <- 5;
# create a new matrix filled with 0
m1 <- matrix(0, mdim[1]+1, mdim[2])
## relative percentage of height
for (i in 1:mdim[2]) { m1[1:mdim[1],i] <- m[,i]/sum(m[,i]) }
## height of each rectangles
m1 <- m1 * height
## vertical position
for (j in (mdim[1]-1):1) { m1[j,] = m1[j,] + m1[j+1,] }
m1[mdim[1]+1,] <- rep(0,mdim[2])
m1 <- m1 + margin
v1 <- m1[2:(mdim[1]+1),]
v2 <- m1[1:mdim[1],] - padding
## width of rectangles
rectwidth = height / mdim[2]
## horizontal positions
h1 <- rep(0, mdim[2])
h2 <- h1
for (i in 1:mdim[2])
{
h1[i] <- margin + (i - 1) * rectwidth
h2[i] <- margin + (i) * rectwidth - padding ## leave a space between two rectangles
}
## an example showing colouring and shading
plot(c(margin, margin+height), c(margin, margin+height), type= "n", xlab="", ylab="", axes=FALSE)
for (i in 1:mdim[2])
{
for (j in 1:mdim[1])
{
rect(h1[i],v1[j,i],h2[i],v2[j,i], col="grey", border="black") # coloured
text(h1[i]+15, v1[j,i]+11, j, col="white");
}
text(h1[i]+15, v2[1,i]+11, xlabs[i])
}
mtext(groupname, side=2, line=0, cex=1.6);
}
To use the function is pretty simple. First create a matrix and then call the brickblock function like the following.
x<-matrix(c(18,8,10,8,14,19,12,3,14,3,11,17,18,7,11,12,64,37,44,40),4)
brickblock(x, 500, c("2CC", "2SC", "1CC", "1SC", "Total"),"Cluster");
It will draw a graph similar to the following.
