> df <- data.frame(numbers = c("123,456,789", "1,234,567", "1,234", "1"))
> df
numbers
1 123,456,789
2 1,234,567
3 1,234
4 1
> df$numbers <- as.numeric(gsub(",","",df$numbers))
> df
numbers
1 123456789
2 1234567
3 1234
4 1