Good day everyone, been trying to find a way to add a column based on conditions inside the same dataframe , for example using mtcars how can I multiply by 2 all the rows that meet condition mpg*cyl=126 and add the result in another column at the end? those that meet the condition will add the result and those that not will put a 0 as a result:
thanks a lot.
It's not clear to me what you mean by "multiply by 2 all the rows", but this works for the condition part.
library(tidyverse)
mtcars %>%
mutate(new_col = if_else(mpg*cyl == 126.0, 2, 0)) %>%
head()
#> mpg cyl disp hp drat wt qsec vs am gear carb new_col
#> 1 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4 2
#> 2 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4 2
#> 3 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1 0
#> 4 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1 0
#> 5 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2 0
#> 6 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1 0
Created on 2019-03-20 by the reprex package (v0.2.1)
I am not sure I got your desired condition correct, but here is one possibility using mutate() from the dplyr package.
library(dplyr)
mtcars <- mtcars %>% mutate( NewCol = ifelse(mpg * cyl >= 126, 2 * mpg * cyl, 0))
Created on 2019-03-20 by the reprex package (v0.2.1)
How to multiply by 2 all the rows that meet condition
mpg*cyl=126and add the result in another column at the end? Those that meet the condition will add the result and those that not will put a 0 as a result.
Hi! It sounds like you're trying to multiply the subset filter(mtcars, mpg * cyl == 126) by 2, zero-fill the subset filter(mtcars, mpg * cyl != 126), and preserve the existing columns in mtcars.
library(tidyverse)
set.seed(321)
group_nest(mtcars, .p = mpg * cyl == 126) %>%
transmute(data,
map_if(data, .p,
~ .x * 2,
.else = ~ mutate_all(.x, ~ 0))) %>%
unnest() %>%
sample_n(5)
#> # A tibble: 5 x 22
#> mpg cyl disp hp drat wt qsec vs am gear carb mpg1
#> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 21 6 160 110 3.9 2.62 16.5 0 1 4 4 42
#> 2 21.4 4 121 109 4.11 2.78 18.6 1 1 4 2 0
#> 3 19.2 6 168. 123 3.92 3.44 18.3 1 0 4 4 0
#> 4 21 6 160 110 3.9 2.88 17.0 0 1 4 4 42
#> 5 17.3 8 276. 180 3.07 3.73 17.6 0 0 3 3 0
#> # … with 10 more variables: cyl1 <dbl>, disp1 <dbl>, hp1 <dbl>,
#> # drat1 <dbl>, wt1 <dbl>, qsec1 <dbl>, vs1 <dbl>, am1 <dbl>,
#> # gear1 <dbl>, carb1 <dbl>
Created on 2019-03-20 by the reprex package (v0.2.1)
Great!, thanks a lot everyone it worked perfectly with the provided examples.
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