A study investigated the condition of two different arteries, harvested from 110 candidates for coronary artery bypass surgery: the radial artery (RA) from the arm, and the internal thoracic artery (ITA) from the chest. In this question, you will look at the outcome “medial calcification of the radial artery” (yes/no), and patient factors which may affect this outcome. It is an important outcome, because radial arteries with medial calcification may not be suitable for use in bypass surgery.

The data is in the filegraft_arteries.csv on the LMS. Read the data into R. The name of the outcome (or response variable) has been shortened toRAcalc.

(a) We will consider two explanatory variables – presence or absence of diabetes, and presence or absence of hypertension. Usingtable(), create a table of the frequencies of the 8 combinations of the response variable and the two explanatory variables.

Using these frequencies, create a data frame suitable for logistic regression. The first of the 4 rows of this data frame should look something like this:

Diabetes Hypertension RAcalc total

no no 4 41