DavoWW
1
I have this user-defined function that works stand-alone but not in a dplyr pipe.
What am I doing wrong?
# Function to add the object name as a new dataframe column, and
# move it to first position
library(tidyverse, quietly=TRUE)
name_as_column <- function(.data) {
object_name <- as.character(substitute(.data))
.data$obj_name <- object_name
y <- "obj_name"
.data <- .data[,c(y, setdiff(names(.data), y))]
return(.data)
}
# Works here
head(name_as_column(mtcars))
#> obj_name mpg cyl disp hp drat wt qsec vs am gear carb
#> Mazda RX4 mtcars 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
#> Mazda RX4 Wag mtcars 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
#> Datsun 710 mtcars 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
#> Hornet 4 Drive mtcars 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
#> Hornet Sportabout mtcars 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
#> Valiant mtcars 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
head(name_as_column(iris))
#> obj_name Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#> 1 iris 5.1 3.5 1.4 0.2 setosa
#> 2 iris 4.9 3.0 1.4 0.2 setosa
#> 3 iris 4.7 3.2 1.3 0.2 setosa
#> 4 iris 4.6 3.1 1.5 0.2 setosa
#> 5 iris 5.0 3.6 1.4 0.2 setosa
#> 6 iris 5.4 3.9 1.7 0.4 setosa
# Doesn't work in dplyr pipe
mtcars %>%
name_as_column(.) %>%
head()
#> obj_name 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
Created on 2021-02-12 by the reprex package (v1.0.0)
lars
4
There's already a handy function available where you can, optionally, provide the new column name.
library(tidyverse)
mtcars %>%
rownames_to_column(var = "obj_name") %>%
head()
#> obj_name mpg cyl disp hp drat wt qsec vs am gear carb
#> 1 Mazda RX4 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
#> 2 Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
#> 3 Datsun 710 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
#> 4 Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
#> 5 Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
#> 6 Valiant 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
Created on 2021-02-12 by the reprex package (v1.0.0)
Is this helpful? Or is your function more intended as an example to get an hand on using your own defined function within pipes?
lars
5
I reread your post and I believe I now better understand what your aim is.
Is the following useful?
library(tidyverse)
name_as_column <- function(.data, obj_name = "not_provided") {
obj_value <- {{obj_name}} %>% as.character()
df <- .data %>%
## add column `obj_name` with `obj_value`
mutate(obj_name = obj_value) %>%
select(obj_name, everything()) %>%
identity()
## return the result
df
}
## make sure to add the dot to the substitute function!
mtcars %>%
name_as_column(obj_name = substitute(.)) %>%
head()
#> obj_name mpg cyl disp hp drat wt qsec vs am gear carb
#> Mazda RX4 mtcars 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
#> Mazda RX4 Wag mtcars 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
#> Datsun 710 mtcars 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
#> Hornet 4 Drive mtcars 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
#> Hornet Sportabout mtcars 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
#> Valiant mtcars 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
mtcars %>%
name_as_column(obj_name = "whatever you prefer") %>%
head()
#> obj_name mpg cyl disp hp drat wt qsec vs am
#> Mazda RX4 whatever you prefer 21.0 6 160 110 3.90 2.620 16.46 0 1
#> Mazda RX4 Wag whatever you prefer 21.0 6 160 110 3.90 2.875 17.02 0 1
#> Datsun 710 whatever you prefer 22.8 4 108 93 3.85 2.320 18.61 1 1
#> Hornet 4 Drive whatever you prefer 21.4 6 258 110 3.08 3.215 19.44 1 0
#> Hornet Sportabout whatever you prefer 18.7 8 360 175 3.15 3.440 17.02 0 0
#> Valiant whatever you prefer 18.1 6 225 105 2.76 3.460 20.22 1 0
#> gear carb
#> Mazda RX4 4 4
#> Mazda RX4 Wag 4 4
#> Datsun 710 4 1
#> Hornet 4 Drive 3 1
#> Hornet Sportabout 3 2
#> Valiant 3 1
## use default value as defined in the function
mtcars %>%
name_as_column() %>%
head()
#> obj_name mpg cyl disp hp drat wt qsec vs am gear
#> Mazda RX4 not_provided 21.0 6 160 110 3.90 2.620 16.46 0 1 4
#> Mazda RX4 Wag not_provided 21.0 6 160 110 3.90 2.875 17.02 0 1 4
#> Datsun 710 not_provided 22.8 4 108 93 3.85 2.320 18.61 1 1 4
#> Hornet 4 Drive not_provided 21.4 6 258 110 3.08 3.215 19.44 1 0 3
#> Hornet Sportabout not_provided 18.7 8 360 175 3.15 3.440 17.02 0 0 3
#> Valiant not_provided 18.1 6 225 105 2.76 3.460 20.22 1 0 3
#> carb
#> Mazda RX4 4
#> Mazda RX4 Wag 4
#> Datsun 710 1
#> Hornet 4 Drive 1
#> Hornet Sportabout 2
#> Valiant 1
Created on 2021-02-12 by the reprex package (v1.0.0)
DavoWW
6
Hi @lars,
Many thanks for your suggestions.
I have settled on this compromise which provides a message about use of this function in a pipe:
name_as_column <- function(.data, obj_name = "") {
require(dplyr)
if(obj_name=="") {
message("Did you mean to use 'name_as_column(obj_name=substitute(.))' in a pipe?")
obj_name <- "not_provided"
}
obj_value <- {{obj_name}} %>% as.character()
df <- .data %>%
mutate(obj_name = obj_value) %>%
select(obj_name, everything())
return(df)
}
head(name_as_column(mtcars))
#> Loading required package: dplyr
#>
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#>
#> filter, lag
#> The following objects are masked from 'package:base':
#>
#> intersect, setdiff, setequal, union
#> Did you mean to use 'name_as_column(obj_name=substitute(.))' in a pipe?
#> obj_name mpg cyl disp hp drat wt qsec vs am gear
#> Mazda RX4 not_provided 21.0 6 160 110 3.90 2.620 16.46 0 1 4
#> Mazda RX4 Wag not_provided 21.0 6 160 110 3.90 2.875 17.02 0 1 4
#> Datsun 710 not_provided 22.8 4 108 93 3.85 2.320 18.61 1 1 4
#> Hornet 4 Drive not_provided 21.4 6 258 110 3.08 3.215 19.44 1 0 3
#> Hornet Sportabout not_provided 18.7 8 360 175 3.15 3.440 17.02 0 0 3
#> Valiant not_provided 18.1 6 225 105 2.76 3.460 20.22 1 0 3
#> carb
#> Mazda RX4 4
#> Mazda RX4 Wag 4
#> Datsun 710 1
#> Hornet 4 Drive 1
#> Hornet Sportabout 2
#> Valiant 1
head(name_as_column(mtcars, obj_name="testing_name"))
#> obj_name mpg cyl disp hp drat wt qsec vs am gear
#> Mazda RX4 testing_name 21.0 6 160 110 3.90 2.620 16.46 0 1 4
#> Mazda RX4 Wag testing_name 21.0 6 160 110 3.90 2.875 17.02 0 1 4
#> Datsun 710 testing_name 22.8 4 108 93 3.85 2.320 18.61 1 1 4
#> Hornet 4 Drive testing_name 21.4 6 258 110 3.08 3.215 19.44 1 0 3
#> Hornet Sportabout testing_name 18.7 8 360 175 3.15 3.440 17.02 0 0 3
#> Valiant testing_name 18.1 6 225 105 2.76 3.460 20.22 1 0 3
#> carb
#> Mazda RX4 4
#> Mazda RX4 Wag 4
#> Datsun 710 1
#> Hornet 4 Drive 1
#> Hornet Sportabout 2
#> Valiant 1
mtcars %>%
name_as_column(obj_name=substitute(.)) %>%
head()
#> obj_name mpg cyl disp hp drat wt qsec vs am gear carb
#> Mazda RX4 mtcars 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
#> Mazda RX4 Wag mtcars 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
#> Datsun 710 mtcars 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
#> Hornet 4 Drive mtcars 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
#> Hornet Sportabout mtcars 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
#> Valiant mtcars 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
mtcars %>%
name_as_column() %>%
head()
#> Did you mean to use 'name_as_column(obj_name=substitute(.))' in a pipe?
#> obj_name mpg cyl disp hp drat wt qsec vs am gear
#> Mazda RX4 not_provided 21.0 6 160 110 3.90 2.620 16.46 0 1 4
#> Mazda RX4 Wag not_provided 21.0 6 160 110 3.90 2.875 17.02 0 1 4
#> Datsun 710 not_provided 22.8 4 108 93 3.85 2.320 18.61 1 1 4
#> Hornet 4 Drive not_provided 21.4 6 258 110 3.08 3.215 19.44 1 0 3
#> Hornet Sportabout not_provided 18.7 8 360 175 3.15 3.440 17.02 0 0 3
#> Valiant not_provided 18.1 6 225 105 2.76 3.460 20.22 1 0 3
#> carb
#> Mazda RX4 4
#> Mazda RX4 Wag 4
#> Datsun 710 1
#> Hornet 4 Drive 1
#> Hornet Sportabout 2
#> Valiant 1
Created on 2021-02-13 by the reprex package (v1.0.0)
1 Like
DavoWW
7
Hi @Yarnabrina,
Thanks for your suggestions. I couldn't make progress with this approach but see my response to @lars.
system
Closed
8
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