I am trying to improve the clarity and aspect of a histogram of discrete values which I need to represent with a log scale.
Please consider the following MWE
set.seed(99)
data <- data.frame(dist = as.integer(rlnorm(1000, sdlog = 2)))
class(data$dist)
ggplot(data, aes(x=dist)) + geom_histogram()
which produces
and then
ggplot(data, aes(x=dist)) + geom_line() + scale_x_log10(breaks=c(1,2,3,4,5,10,100))
which probably is even worse
since now it gives the impression that the something is missing between "1" and "2", and also is not totally clear which bar has value "1" (bar is on the right of the tick) and which bar has value "2" (bar is on the left of the tick).
I understand that technically ggplot provides the "right" visual answer for a log scale. Yet as observer I have some problem in understanding it.
Is it possible to improve something?
EDIT:
This what happen when I applied Jaap solution to my real data
Where do the dips between x=0 and x=1 and between x=1 and x=2 come from? My value are discrete, but then why the plot is also mapping x=1.5 and x=2.5?
This can be done easily using the ggplot2 functions scale_x_continuous() and scale_y_continuous(), which make it possible to set log2 or log10 axis scale. An other possibility is the function scale_x_log10() and scale_y_log10(), which transform, respectively, the x and y axis scales into a log scale: base 10.
To change the number of bins in the histogram using the ggplot2 package library in the R Language, we use the bins argument of the geom_histogram() function. The bins argument of the geom_histogram() function to manually set the number of bars, cells, or bins the whole histogram will be divided into.
In a previous blog post, you learned how to make histograms with the hist() function. You can also make histograms by using ggplot2 , “a plotting system for R, based on the grammar of graphics” that was created by Hadley Wickham.
The first thing that comes to mind, is playing with the binwidth
. But that doesn't give a great solution either:
ggplot(data, aes(x=dist)) +
geom_histogram(binwidth=10) +
scale_x_continuous(expand=c(0,0)) +
scale_y_continuous(expand=c(0.015,0)) +
theme_bw()
gives:
In this case it is probably better to use a density plot. However, when you use scale_x_log10
you will get a warning message (Removed 524 rows containing non-finite values (stat_density)
). This can be resolved by using a log plus one transformation.
The following code:
library(ggplot2)
library(scales)
ggplot(data, aes(x=dist)) +
stat_density(aes(y=..count..), color="black", fill="blue", alpha=0.3) +
scale_x_continuous(breaks=c(0,1,2,3,4,5,10,30,100,300,1000), trans="log1p", expand=c(0,0)) +
scale_y_continuous(breaks=c(0,125,250,375,500,625,750), expand=c(0,0)) +
theme_bw()
will give this result:
I am wondering, what if, y-axis is scaled instead of x-axis. It will results into few warnings wherever values are 0, but may serve your purpose.
set.seed(99)
data <- data.frame(dist = as.integer(rlnorm(1000, sdlog = 2)))
class(data$dist)
ggplot(data, aes(x=dist)) + geom_histogram() + scale_y_log10()
Also you may want to display frequencies as data labels, since people might ignore the y-scale and it takes some time to realize that y scale is logarithmic.
ggplot(data, aes(x=dist)) + geom_histogram(fill = 'skyblue', color = 'grey30') + scale_y_log10() +
stat_bin(geom="text", size=3.5, aes(label=..count.., y=0.8*(..count..)))
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