CODEWITHSUNDEEP
rggplot2histogram
dalloliogm
dalloliogm

Reputation: 8940

ggplot2: plotting multiple histograms in the same page, but one with inverted coordinates

I would like to plot two or more histograms from the same data, but inverting the coordinates of one group, like the following:

enter image description here

(note: this figure is taken from Grossman et al 2011, A composite of Multiple Signals Distinguishes Causal Variants in Regions of Positive Selection)

For example, let's take the diamonds dataset from ggplot2:

> library(ggplot2)
> head(diamonds)
  carat       cut color clarity depth table price    x    y    z
1  0.23     Ideal     E     SI2  61.5    55   326 3.95 3.98 2.43
2  0.21   Premium     E     SI1  59.8    61   326 3.89 3.84 2.31
3  0.23      Good     E     VS1  56.9    65   327 4.05 4.07 2.31
4  0.29   Premium     I     VS2  62.4    58   334 4.20 4.23 2.63
5  0.31      Good     J     SI2  63.3    58   335 4.34 4.35 2.75
6  0.24 Very Good     J    VVS2  62.8    57   336 3.94 3.96 2.48

One approach I have tried has been to calculate the histogram using stat_bin without plotting it, changing the values of the counts column returned by it. 

> my_sb <-stat_bin(data=diamonds, mapping=aes(x=x)

The documentation of stat_bin says that this function should return a data.frame equal to the mapped one, but adding four new columns (count, density, ncount, ndensity). However, I can not find these columns anywhere:

# I supposed that this should contain a count, density columns, but it does not.
> print(head(my_sb$data))  
  carat       cut color clarity depth table price    x    y    z
1  0.23     Ideal     E     SI2  61.5    55   326 3.95 3.98 2.43
2  0.21   Premium     E     SI1  59.8    61   326 3.89 3.84 2.31
3  0.23      Good     E     VS1  56.9    65   327 4.05 4.07 2.31
4  0.29   Premium     I     VS2  62.4    58   334 4.20 4.23 2.63
5  0.31      Good     J     SI2  63.3    58   335 4.34 4.35 2.75
6  0.24 Very Good     J    VVS2  62.8    57   336 3.94 3.96 2.48

Another possible approach is to use scale_y_reverse(), but I don't know how to apply it to a single dataset.

The third approach that I can think of is to use viewPorts, but I am not quite sure on how to implement it.

Upvotes: 4

Views: 2013

Answers (1)

joran
joran

Reputation: 173737

Like this maybe:

ggplot(data = diamonds) + 
    geom_histogram(aes(x = x,y = ..count..)) + 
    geom_histogram(aes(x = x,y = -..count..))

FYI - I couldn't remember exactly how I'd done this in the past, so I Googled "ggplot2 inverted histogram" and clicked on the first hit, a StackOverflow question.

I'm not sure exactly how the proto object that stat_bin returns is structured, but the new variables are in there somewhere. The way this works is that geom_histogram itself calls stat_bin to perform the binning, and so it has access to the computed variables, which we can map to the y variable.

Upvotes: 5

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