I need ggplot scale_x_log10() to give me both negative and positive numbers as output

Question

I generate a fine histogram here with both positive and negative numbers.

x <- rnorm(5000,0,1000)
library(ggplot2)
df <- data.frame(x)
ggplot(df, aes(x = x)) + geom_histogram()

What I want is to have a logged x-axis. When I do this for only positive numbers with scale_x_log10(), it works like a charm. But here it does not and it either removes my negative numbers are adds them to the positive numbers.

ggplot(df, aes(x = x)) + geom_histogram() + scale_x_log10()

All I really want is for the ticks and the spacing between the ticks to follow the log pattern and for either side of 0 on the x-axis to be mirror images of each other but I cannot seem to get that.

You can't take the logarithm of a negative number, which is why ggplot is cutting off your axis. — Michael Gao, May 25 '16 at 19:50
This answer might help: http://stackoverflow.com/questions/14504869/histogram-with-negative-logarithmic-scale-in-r — Mhairi McNeill, May 25 '16 at 20:02
Perhaps a signed square root would be a more appropriate transformation? — Gregor Thomas, May 25 '16 at 20:05
@MhairiMcNeill Sadly I already read that and it did not. Thanks anyway — James Lloyd, May 25 '16 at 20:31
@MichaelGao, I get that, but I feel there should be an equivalent thing to get a plot to look the way I want. I have seen such plots but I do not know how to get them. — James Lloyd, May 25 '16 at 20:32
well, where have you seen such plots? Can you provide a link/description of what they did? — Ben Bolker, May 25 '16 at 21:47

score 16 · Answer 1 · edited May 23 '17 at 12:17

This is possible to do by defining a new transformation (a "signed log", sign(x)*log(abs(x)); the asinh transformation suggested by Histogram with "negative" logarithmic scale in R might be more principled, or a signed square root as suggested in the comments above), but I question whether it's a good idea or not. Nevertheless ... ("Teach a man to fish and you feed him for a lifetime; give him a rope, and he can go hang himself ...") ... you can define your own axis transformations via trans_new as shown below.

Setup:

library(ggplot2); theme_set(theme_bw())
set.seed(101)
df <- data.frame(x=rnorm(5000,0,1000))

Set up the new transformation:

weird <- scales::trans_new("signed_log",
       transform=function(x) sign(x)*log(abs(x)),
       inverse=function(x) sign(x)*exp(abs(x)))

Try it out -- first on the raw points:

ggplot(df,aes(x,x))+geom_point()+
    scale_y_continuous(trans=weird)

Now on the histogram:

ggplot(df, aes(x = x)) + geom_histogram()+
    scale_x_continuous(trans=weird)

Things you should worry about:

this transformation is going to be nonsensical when you have values between -1 and 1
you might have to worry about transforming the axis of a histogram without scaling bin height appropriately: it may give you a misleading impression of the probability density -- although in this case ggplot(df, aes(x = weird$transform(x))) + geom_histogram() looks about the same as the plot above ...

Thank you. When I try to apply this to some code that I am calling a column in a complex dataframe, the $ is giving an error in the `weird <- scales::trans_new("signed_log", transform=function(x) sign(x)*log(abs(x)), inverse=function(x) sign(x)*exp(abs(x)))` part of the code — James Lloyd, May 25 '16 at 20:48
I'm sorry, but that's not enough information for me to troubleshoot your problem. If you just want to do the transformation outside ggplot (which would be simpler), define `signedlog <- function(x) sign(x)*log(abs(x))` — Ben Bolker, May 25 '16 at 21:46
I would also consider using `log1p` and `expm1` in the transform. — Eli Korvigo, Oct 07 '18 at 17:06

Fkiran · Answer 2 · 2022-12-23T03:32:00.663

0

This works with small numbers!

if (require("lme4") && require("glmmTMB")) { 
weird <- scales::trans_new("signed_log",
       transform=function(x) sign(x)*log1p(abs(x)),
       inverse=function(x) sign(x)*expm1(abs(x)))

p<- plot_model(fit.me.model)

p+ scale_y_continuous(trans=weird)
}

r randomeffects lme4 glmmtmb

edited Dec 23 '22 at 03:32

answered Dec 19 '22 at 22:23

Fkiran

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I need ggplot scale_x_log10() to give me both negative and positive numbers as output

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