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With mtcars for example, I'd like to create a new column carb_dots such that when carb = 4, carb_dots = "...."
Using dplyr, I've tried
library(dplyr)
mtcars2 <- mtcars %>% mutate(carb_dots = rep(".", carb))
This errors with
Error in mutate_impl(.data, dots) : Evaluation error: invalid 'times' argument.
What should I do? Thanks for your suggestions.
379
dplyr - R function to add multiple new columns based on values from a group of columns - Stack Overflow.
We can create two or more new variables using a single mutate function. For example, to create two new columns, we use mutate() fucntions with new variables separated by comma.
In R programming, the mutate function is used to create a new variable from a data set. In order to use the function, we need to install the dplyr package, which is an add-on to R that includes a host of cool functions for selecting, filtering, grouping, and arranging data.
With the addition of stringr, you can do:
mtcars %>%
mutate(carb_dots = str_dup(".", carb))
mpg cyl disp hp drat wt qsec vs am gear carb carb_dots
1 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4 ....
2 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4 ....
3 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1 .
4 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1 .
5 18.7 8 360.0 175 3.15 3.440 17.02 0 0 3 2 ..
6 18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1 .
7 14.3 8 360.0 245 3.21 3.570 15.84 0 0 3 4 ....
8 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2 ..
9 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2 ..
10 19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4 ....
We can use strrep
library(dplyr)
mtcars %>%
mutate(carb_dots = strrep(".", carb))
# mpg cyl disp hp drat wt qsec vs am gear carb carb_dots
#Mazda RX4 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4 ....
#Mazda RX4 Wag 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4 ....
#Datsun 710 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1 .
#Hornet 4 Drive 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1 .
#Hornet Sportabout 18.7 8 360.0 175 3.15 3.440 17.02 0 0 3 2 ..
#Valiant 18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1 .
#Duster 360 14.3 8 360.0 245 3.21 3.570 15.84 0 0 3 4 ....
#...
If we need to use rep
mtcars %>%
rowwise %>%
mutate(carb_dots = paste(rep(".", carb), collapse=""))
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