Creating scatterplot matrices

Scatterplot matrices of bivariate data are helpful to identify relationships between variables in a dataset. We can create scatterplot matrices using pairs() and the tilde sign, along with plus signs that instruct R to include the desired variables:

pairs(~WEIGHT_1 + WEIGHT_2 + HEIGHT, data=T, 
main="Scatterplot Matrix of Medical Data")

This syntax gives the following matrix:

If we want a smooth curve (LOWESS) in each bivariate plot, we include the argument panel=panel.smooth:

pairs(~WEIGHT_1 + WEIGHT_2 + HEIGHT, data=T, 
main="Scatterplot Matrix of Medical Data", panel = panel.smooth)

The matrix obtained is as follows:

We see a strong linear relationship between WEIGHT_1 and WEIGHT_2, and curved relationships between those variables and HEIGHT.

Writing functions to create graphs

Why not create functions to draw graphs? Here's a function for histograms of vectors of data with standard titles and labels. It allows you to add numbers to the title and axis labels and...