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I would like to use mutate to add new columns to a data.frame based on specific colums divided by another column and keep the originalname plus a fixed pattern.

mtcars$mpg_HorsePower = mtcars$mpg / mtcars$hp
mtcars$cyl_HorsePower = mtcars$cyl / mtcars$hp
mtcars$disp_HorsePower = mtcars$disp / mtcars$hp
head(mtcars)
#                    mpg cyl disp  hp drat    wt  qsec vs am gear carb mpg_HorsePower cyl_HorsePower disp_HorsePower
# Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4      0.1909091     0.05454545        1.454545
# Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4      0.1909091     0.05454545        1.454545
# Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1      0.2451613     0.04301075        1.161290
# Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1      0.1945455     0.05454545        2.345455
# Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2      0.1068571     0.04571429        2.057143
# Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1      0.1723810     0.05714286        2.142857

I was hoping that something like this

mtcars %>% 
  mutate_at(vars(mpg:disp), funs(. / hp))

would work but does nothing.

stefan
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candelas762
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    This would have worked: `mtcars %>% mutate_at(vars(mpg:disp), list(HorsePower = ~. / hp))` but `across` is now the preferred method rather than `mutate_at` – MrFlick Nov 28 '22 at 14:31
  • Why is it preferred now? – candelas762 Nov 29 '22 at 08:47
  • As indicated on the current `?mutate_at` help page, the function has been superseded. The package authors believe that `across` is a better way to solve the problem and is more consistently used with other verbs as well. I don't think there are any immediate plans to deprecate the function but it may not be well supported in the future. – MrFlick Nov 29 '22 at 14:12

1 Answers1

2

Using dplyr::across you could achieve your desired result like so:

library(dplyr, w = FALSE)

mtcars2 <- mtcars %>% 
  mutate(across(mpg:disp, list(Horsepower = ~. / hp)))

head(mtcars2)
#>                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
#> Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
#> Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
#> Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
#> Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
#> Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
#> Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1
#>                   mpg_Horsepower cyl_Horsepower disp_Horsepower
#> Mazda RX4              0.1909091     0.05454545        1.454545
#> Mazda RX4 Wag          0.1909091     0.05454545        1.454545
#> Datsun 710             0.2451613     0.04301075        1.161290
#> Hornet 4 Drive         0.1945455     0.05454545        2.345455
#> Hornet Sportabout      0.1068571     0.04571429        2.057143
#> Valiant                0.1723810     0.05714286        2.142857
stefan
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