Data Analysis with R, Second Edition - Second Edition

The relationship between two continuous variables

Do you think that there is a relationship between women's heights and their weights? If you said yes, congratulations, you're right!

We can verify this assertion using the data in R's built-in dataset, women, which holds the height and weight of 15 American women from ages 30 to 39:

 head(women) 
    height weight 
  1     58    115 
  2     59    117 
  3     60    120 
  4     61    123 
  5     62    126 
  6     63    129 
 nrow(women) 
  [1] 15 

Specifically, this relationship is referred to as a positive relationship, because as one of the variable increases, we expect an increase in the other variable.

The most typical visual representation of the relationship between two continuous variables is a scatterplot.

A scatterplot is displayed as a group of ...