Tornado plot in R

Question

I am trying to make a tornado plot (a.k.a. sensitivity graph) in R. The goal is to visualize the effect of a 10% increase and 10% decrease in some variables.

So far I have gotten this result

This is the code I am using:

# Tornado plot

data <- matrix(c(-0.02,0.02,-0.01,0.01,-0.03,0.02,-0.01,0.04), ncol = 4)
rownames(data) <- c('+10%','-10%')                       # Amount of change in variables
colnames(data) <- c('V_bar', 'alpha', 'rho','xi')        # Names of variables
x <- seq(-0.04,0.04, length=10)                          # For plotting '%' on x-axis

barplot(data, horiz = T, las=1, xlim = c(-0.04,0.04), xaxt='n', ylab = '',
        beside=T, col=c('springgreen','indianred2'))
axis(1, at=pretty(x),  lab=paste0(pretty(x) * 100," %"), las=TRUE)

I have two final goals I want to achieve:

1. Getting the bars aligned for each variable (not juxaposed as they are now). In other words, the green and red side of each variable bar should meet at the center, giving a total of four bars.

2. Paste mathematical characters (instead of the text) on the y-axis. The "V_bar" column should be a V with a bar on top.

Edit: I have posted a separate question for the mathematical characters: Barplot: Greek letters on y axis in R

Answer 1

So you can split the positive and negative case and plot the overlaying each other with add = TRUE

barplot(data[1,], horiz = T, las=1, xlim = c(-0.04,0.04), xaxt='n', ylab = '',
        beside=T, col=c('springgreen'))
barplot(data[2,], horiz = T, las=1, xlim = c(-0.04,0.04), xaxt='n', ylab = '',
        beside=T, col=c('indianred2'), add = TRUE)
axis(1, at=pretty(x),  lab=paste0(pretty(x) * 100," %"), las=TRUE)

so we are taking the first row (negative values) for one plot, and the second row (positive values) for second plot. Their order must match and they will be plotted side by side.

For this to work and match nicely results must have the same length and only one colour per graph is specified.

Adding greek character to axis title

this other post might help you with your second question