Apply jitter uniformly across geoms in ggplot2

user_4181415 0
Viewed 547

I would like to jitter two geoms by the same amount. Consider the following minimal example:

library(ggplot2)
pdat <- data.frame(x = c(1,1,2,2,4,4,8,8),
                   y = c(1,1.1,2,2.2,3,3.3,4,4.4),
                   ymin = c(1,1.1,2,2.2,3,3.3,4,4.4)-.9^(0:7),           
                   ymax = c(1,1.1,2,2.2,3,3.3,4,4.4)+.9^(0:7),
                   colour = as.factor(rep(1:2,4)))

ggplot(pdat, aes(x=x,y=y,ymin=ymin,ymax=ymax,color=colour)) + 
    geom_linerange(position='jitter') + geom_point(position='jitter')

ggplot(pdat, aes(x=jitter(x),y=y,ymin=ymin,ymax=ymax,color=colour)) + 
    geom_linerange() + geom_point()

which produces the following plots: ggplots

In both cases, the jittering is random across geoms (the points and lineranges are in different locations), whereas I would like them to be consistent for each data point (the points in the middles of the corresponding lineranges). Is this possible?

Note that I would not consider manually adding noise to the x variable to be a solution as this would destroy the ability to apply coordinate transformations. E.g., defining pdat$x2 <- pdat$x+rnorm(8)/10,

ggplot(pdat, aes(x=x2,y=y,ymin=ymin,ymax=ymax,color=colour)) + 
    geom_linerange() + geom_point()

looks good, but then the variance of the jitter is subject to any subsequent transformations as can be seen in 

ggplot(pdat,aes(x=x2,y=y,ymin=ymin,ymax=ymax,color=colour)) + 
    geom_linerange() + geom_point() + scale_x_log10()
ggplot2 r
1 Answers

Using position_jitter function, you can add a seed value to get reproducible jitter effect:

library(ggplot2)

ggplot(pdat, aes(x = x, y = y, ymin = ymin, ymax = ymax, color = colour))+
  geom_point(position = position_jitter(seed = 123, width =0.2))+
  geom_linerange(position = position_jitter(seed = 123, width = 0.2))

enter image description here

Does it answer your question ?

user_122598530
Related