Remove rows where all values of a column are identical, based on another column [duplicate]

Answer 1

A base R solution,

df[!with(df, ave(info, id, FUN = function(i)var(i) == 0)),]
#slightly different syntax (as per @lmo)
#df[ave(df$info, df$id, FUN=var) > 0,]

which gives,

  id info
3  2    0
4  2   10