Checking the dimensions of your data

We are going to start out using the mtcars data set, which contains measures of design, performance and consumption for different cars. If we want to know how many cases and variables there are in the data set we could count them manually, but this could take a very long time. A faster way is to use the function dim$().$ The first value returned by dim$()$ is the number of cases $($rows$)$ and the second value is the number of variables $($columns$).$

The variables in mtcars are as follows:

$[,1]$ mpg Miles$/($US$)$ gallon.

$[,2]$ cyl Number of cylinders.

$[,3]$ disp Displacement $($cu$.$in$.)$

$[,4]$ hp Gross horsepower

$[,5]$ drat Rear axle ratio

$[,6]$ wt Weight $($lb$/1000)$

$[,7]$ qsec $1/4$ mile time

$[,8]$ vs V$/$S

$[,9]$ am Transmission $(0=$ automatic, $1=$ manual$)$

$[,10]$ gear Number of forward gears

$[,11]$ carb Number of carburetors