How to convert certain columns only to numeric?

Question

How can I convert certain columns only in a data frame to numeric?

For instance, I have this data frame:

structure(list(airport = c(         


        

Answer 1

Using dplyr:

library(dplyr)
df %>% 
  mutate_at(vars(ws, wd, humidity), as.numeric)

# A tibble: 2 x 5
airport xdate         ws    wd humidity
                
1 EGLL    2016-07-28    6.  237.      68.
2 EGLL    2016-07-31    5.  299.      55.