Replace 0s with NA in tables

问题

I generally work with dataframes and could easily do this for a data frame but on my current project I have the need to replace all zeros with NAs in a table structure. For the following two tables (one using table and the other using ftable) how could I replace all zero counts with NA?

x <- with(mtcars,table(am, gear, cyl, vs))

x2 <- with(mtcars,ftable(am, gear, cyl, vs))

回答1:

This should work:

x[x==0] <- NA

来源：https://stackoverflow.com/questions/9822897/replace-0s-with-na-in-tables