a more general version of `ifelse` in R?

Question

This is a context where the current version of ifelse in R is appropriate:

score <- NULL
x <- "not available"
y <- "available"

ifelse(is.null(score), x, y)
#> [1] "not available"

But what if I want to use something like ifelse to assign other objects. For example, here I would like to assign dataframes, but the current vectorized version returns the first element (column) of the dataframe instead of the entire dataframe.

score <- NULL
x <- iris
y <- mtcars

ifelse(is.null(score), x, y)
#> [[1]]
#>   [1] 5.1 4.9 4.7 4.6 5.0 5.4 4.6 5.0 4.4 4.9 5.4 4.8 4.8 4.3 5.8 5.7 5.4 5.1
#>  [19] 5.7 5.1 5.4 5.1 4.6 5.1 4.8 5.0 5.0 5.2 5.2 4.7 4.8 5.4 5.2 5.5 4.9 5.0
#>  [37] 5.5 4.9 4.4 5.1 5.0 4.5 4.4 5.0 5.1 4.8 5.1 4.6 5.3 5.0 7.0 6.4 6.9 5.5
#>  [55] 6.5 5.7 6.3 4.9 6.6 5.2 5.0 5.9 6.0 6.1 5.6 6.7 5.6 5.8 6.2 5.6 5.9 6.1
#>  [73] 6.3 6.1 6.4 6.6 6.8 6.7 6.0 5.7 5.5 5.5 5.8 6.0 5.4 6.0 6.7 6.3 5.6 5.5
#>  [91] 5.5 6.1 5.8 5.0 5.6 5.7 5.7 6.2 5.1 5.7 6.3 5.8 7.1 6.3 6.5 7.6 4.9 7.3
#> [109] 6.7 7.2 6.5 6.4 6.8 5.7 5.8 6.4 6.5 7.7 7.7 6.0 6.9 5.6 7.7 6.3 6.7 7.2
#> [127] 6.2 6.1 6.4 7.2 7.4 7.9 6.4 6.3 6.1 7.7 6.3 6.4 6.0 6.9 6.7 6.9 5.8 6.8
#> [145] 6.7 6.7 6.3 6.5 6.2 5.9

So I was wondering if there is a general version of ifelse in R that can do something similar.

if statement r

slava-kohut · Answer

You can use switch for this purpose.
For example,
a <- NULL
b <- 1

switch (-1*is.null(a)+2, mtcars, iris)

will return mrcars
switch (-1*is.null(b)+2, mtcars, iris)

will return iris

ThomasIsCoding · Answer

I am not sure if the following code is in your favor
list(iris,mtcars)[[is.null(score)+1]]

akrun · Answer

The ifelse requires all elements to have the same length.  The length of data.frame are the number of columns (as it is a list with columns as elements).  We could wrap it in a list and then the length will be 1 for test, yes and no
ifelse(is.null(score), list(x), list(y))

Allan Cameron · Answer

You can just use if(test) A else B: score <- NULL result <- if(is.null(score)) mtcars else iris head(result) #> 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 score <- 1 result <- if(is.null(score)) mtcars else iris head(result) #> Sepal.Length Sepal.Width Petal.Length Petal.Width Species #> 1 5.1 3.5 1.4 0.2 setosa #> 2 4.9 3.0 1.4 0.2 setosa #> 3 4.7 3.2 1.3 0.2 setosa #> 4 4.6 3.1 1.5 0.2 setosa #> 5 5.0 3.6 1.4 0.2 setosa #> 6 5.4 3.9 1.7 0.4 setosa Or if you need it vectorized like ifelse you could have: result <- lapply(c(1, 2, 3), function(x) if(x != 2) iris else mtcars) str(result) #> List of 3 #> $ :'data.frame': 150 obs. of 5 variables: #> ..$ Sepal.Length: num [1:150] 5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ... #> ..$ Sepal.Width : num [1:150] 3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ... #> ..$ Petal.Length: num [1:150] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ... #> ..$ Petal.Width : num [1:150] 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ... #> ..$ Species : Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 ... #> $ :'data.frame': 32 obs. of 11 variables: #> ..$ mpg : num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ... #> ..$ cyl : num [1:32] 6 6 4 6 8 6 8 4 4 6 ... #> ..$ disp: num [1:32] 160 160 108 258 360 ... #> ..$ hp : num [1:32] 110 110 93 110 175 105 245 62 95 123 ... #> ..$ drat: num [1:32] 3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ... #> ..$ wt : num [1:32] 2.62 2.88 2.32 3.21 3.44 ... #> ..$ qsec: num [1:32] 16.5 17 18.6 19.4 17 ... #> ..$ vs : num [1:32] 0 0 1 1 0 1 0 1 1 1 ... #> ..$ am : num [1:32] 1 1 1 0 0 0 0 0 0 0 ... #> ..$ gear: num [1:32] 4 4 4 3 3 3 3 4 4 4 ... #> ..$ carb: num [1:32] 4 4 1 1 2 1 4 2 2 4 ... #> $ :'data.frame': 150 obs. of 5 variables: #> ..$ Sepal.Length: num [1:150] 5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ... #> ..$ Sepal.Width : num [1:150] 3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ... #> ..$ Petal.Length: num [1:150] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ... #> ..$ Petal.Width : num [1:150] 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ... #> ..$ Species : Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 ... Created on 2020-07-24 by the reprex package (v0.3.0)

a more general version of `ifelse` in R?

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