problem-4.10
problem-4.10
The data set is stored in a matrix, so we can reverse the years
using indexing.
> barplot(t(dvdsales[7:1,]), beside=TRUE)
Using apply() on the rows, we get the yearly amounts:
> apply(dvdsales, 1, sum)
2004 2003 2002 2001 2000 1999 1998
NA 21994389 17089823 12706584 8498545 4019389 1089261
1997
NA
> apply(dvdsales, 1, function(x) sum(x,na.rm=TRUE)) # avoid NA
2004 2003 2002 2001 2000 1999 1998
5957387 21994389 17089823 12706584 8498545 4019389 1089261
1997
315136
Applying sum() to the columns gives the monthly sales. We do
so only for years that have complete data.
> apply(dvdsales[2:6,], 2, sum)
JAN FEB MAR APR MAY JUN JUL AUG
2407354 2545896 4761189 3677919 3539725 5634658 3521254 3812934
SEP OCT NOV DEC
8362963 7551936 9323618 9169284
November is the big winner. (Christmas shopping?)