# problem-3.3

problem-3.3 We can tabulate the coins then multiply by the amounts to find the total amount of money in the change bin.

    > table(coins$value)
    0.01 0.05  0.1 0.25
     203   59   42   67
    > table(coins$value) * c(0.01, 0.05, 0.1, 0.25)
     0.01  0.05   0.1  0.25
     2.03  2.95  4.20 16.75
    > sum(table(coins$value) * c(0.01, 0.05, 0.1, 0.25))
    [1] 25.58

The barplot can be produced with the command

    > barplot(table(coins$year))

It shows a generally increasing trend, as it is more likely to contain more recent coins. Finally, to get the coins by decade, a first attempt would be to try

    > table(cut(coins$year, breaks = seq(1920,2010,by=10)))

But this has ranges like 1921-1930. Using the argument right=FALSE will cause the intervals to take the form [a,b), for example, 1920-1929.