Question

R Language

Use the state.x77 data matrix and the tapply() function to obtain:

(1)   The number of the states in each region.

(2)   The names of the states in each division.

(3)   The median high school graduation rates for groups of states defined by combinations of the factors state.region and state.size.

Answer 1

(1)  use tapply on the vectors state.name and state.region against the function length

##     Northeast         South North Central          West 
##             9            16            12            13

(3) use the vectors HS Grad as the first argument and the list state.region and state.size as the second argument against the function median.

##               Small Medium Large
## Northeast      55.9  56.00 51.45
## South          48.1  41.30 47.40
## North Central  53.3  54.50 52.90
## West           62.4  61.75 62.60