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A histogram is a useful way to visualize the distribution of values for a given variable.
To create a histogram for one variable in R, you can use the hist() function. And to create a histogram for two variables in R, you can use the following syntax:
hist(variable1, col='red') hist(variable2, col='blue', add=TRUE)
The following example shows how to use this syntax in practice.
Example: Create a Histogram of Two Variables in R
The following code shows how to create a histogram of two variables in R:
#make this example reproducible set.seed(1) #define data x1 = rnorm(1000, mean=0.6, sd=0.1) x2 = rnorm(1000, mean=0.4, sd=0.1) #plot two histograms in same graph hist(x1, col='red') hist(x2, col='blue', add=TRUE)
Since the values of the histograms overlap, it’s a good idea to use rgb() colors with increased transparency:
#make this example reproducible set.seed(1) #define data x1 = rnorm(1000, mean=0.6, sd=0.1) x2 = rnorm(1000, mean=0.4, sd=0.1) #plot two histograms in same graph hist(x1, col=rgb(0,0,1,0.2), xlim=c(0, 1), xlab='Values', ylab='Frequency', main='Histogram for two variables') hist(x2, col=rgb(1,0,0,0.2), add=TRUE)
You can also add a legend to make the histograms easier to interpret:
#make this example reproducible set.seed(1) #define data x1 = rnorm(1000, mean=0.6, sd=0.1) x2 = rnorm(1000, mean=0.4, sd=0.1) #plot two histograms in same graph hist(x1, col=rgb(0,0,1,0.2), xlim=c(0, 1), xlab='Values', ylab='Frequency', main='Histogram for two variables') hist(x2, col=rgb(1,0,0,0.2), add=TRUE) #add legend legend('topright', c('Variable 1', 'Variable 2'), fill=c(rgb(0,0,1,0.2), rgb(1,0,0,0.2)))
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