# median
x <-c(10,12,14,16,18,20,22)
f <-c(2,5,12,20,10,7,3)
N <-print(sum(f))
lcf <-print(cumsum(f))
df <-print(data.frame(x,f,lcf))
median_index <-print(which(lcf>=N/2)[1])
median <-print(x[median_index])