Data frames and Combinations

Create a list containing two columns with a count form 1 to 31

L<-list(A=c(1:31),B=c(1:31))

Create a data frame that contains all the combinations 1 to 31 G<-expand.grid(L)

Add a column, excel style:

G$fraction <- G$A/G$B

Filter by column:

G[G$fraction <= 1,]

Count the number of rows of a dataframe:

nrow (G[G$fraction <= 1,])