CODEWITHSUNDEEP
rplot
Alex
Alex

Reputation: 4180

How to plot mirror plots? (Two plots sharing the same x-axis, but one is upside down - below the axis)

Suppose I have two samples that I would like to compare graphically. One way to do it is to lay one over another like below:

x1 = rnorm(100)
x2 = rnorm(100, mean=2)
plot(density(x1))
lines(density(x2), col="red")

I wonder however if there is a way to plot x2 such that the plot shares the same axis as the plot of x1, except that it is upside down, like the plot below. It would be especially great if there is any method that does not involve downloading additional packages.

enter image description here

Thanks!

Upvotes: 0

Views: 4596

Answers (3)

yholtz
yholtz

Reputation: 93

It is possible to get only one x-axis using the mar argument of the par function. The R code would look like this: 

   #Create Data
    x1 = rnorm(100)
    x2 = rnorm(100, mean=2)

    #Make the plot
    par(mfrow=c(2,1))
    par(mar=c(0,5,3,3))
    plot(density(x1) , main="" , xlab="", ylim=c(0,1) , xaxt="n", las=1 , col="slateblue1" , lwd=4 )
    par(mar=c(5,5,0,3))
    plot(density(x2) , main="" , xlab="Value of my variable", ylim=c(1,0) , las=1 , col="tomato3" , lwd=4)

Giving this plot:

1

This graph is present in the R graph gallery

Upvotes: 0

Sven Hohenstein
Sven Hohenstein

Reputation: 81733

If it doesn't matter if the y-axis contains values below zero, you can use this:

x1 <- rnorm(100)
x2 <- rnorm(100, mean=2)
dens1 <- density(x1)
dens2 <- density(x2)
dens2$y <- dens2$y * -1
plot(dens1, 
     ylim = range(c(dens1$y, dens2$y)),
     xlim = range(c(dens1$x, dens2$x)),
     main = "",
     xlab = "")
lines(dens2, col = "red")

densitys

Upvotes: 4

Andrie
Andrie

Reputation: 179558

You can reverse the axis of a plot by using the argument ylim=(...) (or xlim=(...)) and specifying the limits in the reverse order.

For example:

layout(matrix(1:2, ncol=1))
par(mai=c(0.5, 1, 0.5, 1))

plot(c(-6, 6), 0:1, type="n", ylim=c(0, 1), xlab="", ylab="")
lines(density(x1), ylim=c(0, 1))

plot(c(-6, 6), 0:1, type="n", ylim=c(1, 0), xlab="", ylab="")
lines(density(x2), col="red", ylim=c(1, 0))

enter image description here

Upvotes: 3

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