Introduction to R

For a quick look at the shape of a distribution, try hist. For example,

hist(data$bmi)

Using arguments, you can control the number of bins and colour of the plot:

hist(data$bmi, breaks=5, col="blue")

Add a proper x-axis label (xlab = “..”) and a heading (main = “..”):

hist(data$bmi, breaks=5, col="blue", xlab="Body mass index (kg/m^2)", main="Histogram of BMI")

Alternatively you might like to see a density plot.  First you must determine the density data, by creating an object (which I have called “dens_bmi” but you could call it what you like). Then plot the desity data.

dens_bmi <- density(data$bmi)

plot(dens_bmi)

Again, you can give the plot a better heading, and colour it:

plot(dens_bmi, main="Density distribution of BMI", col="blue")

You can also ask for the density data by calling the object you just created

dens_bmi

Or perhaps you’d like a more formal test? If so, you can use the Shapiro- Wilk statistic:

shapiro.test(data$bmi)