R函数学习-mutate()

mutate() 给原来的数据框添加新的列，一般添加在后面

flights_sml <- select(flights,
                      year:day,
                      ends_with("delay"),
                      distance,
                      air_time)

mutate(flights_sml,
       gain = arr_delay - dep_delay,
       speed = distance / air_time * 60)
## # A tibble: 336,776 x 9
##     year month   day dep_delay arr_delay distance air_time   gain speed
##    <int> <int> <int>     <dbl>     <dbl>    <dbl>    <dbl>  <dbl> <dbl>
##  1  2013     1     1      2.00     11.0      1400    227     9.00   370
##  2  2013     1     1      4.00     20.0      1416    227    16.0    374
##  3  2013     1     1      2.00     33.0      1089    160    31.0    408
##  4  2013     1     1     -1.00    -18.0      1576    183   -17.0    517
##  5  2013     1     1     -6.00    -25.0       762    116   -19.0    394
##  6  2013     1     1     -4.00     12.0       719    150    16.0    288
##  7  2013     1     1     -5.00     19.0      1065    158    24.0    404
##  8  2013     1     1     -3.00    -14.0       229     53.0 -11.0    259
##  9  2013     1     1     -3.00    - 8.00      944    140   - 5.00   405
## 10  2013     1     1     -2.00      8.00      733    138    10.0    319
## # ... with 336,766 more rows

# 上面的代码可改写成
df <- flights_sml %>% mutate(gain = arr_delay - dep_delay,
       speed = distance / air_time * 60)