I'm working with the mtcars dataset. I'm trying to create a new dataset which contains only the columns that are non-integer. To do this, I've tried several things, mainly trying to use lapply like so:
> newdata <- lapply(mtcars, Negate(is.integer))
But this doesn't return what I need. In the exercise, it was told that which() can help us do this, so I ask - how?
Thanks
Using which() to filter out columns from a dataset
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4 Answers
You can do:
iris[sapply(iris, Negate(is.factor))]
Sepal.Length Sepal.Width Petal.Length Petal.Width
1 5.1 3.5 1.4 0.2
2 4.9 3.0 1.4 0.2
3 4.7 3.2 1.3 0.2
4 4.6 3.1 1.5 0.2
5 5.0 3.6 1.4 0.2
6 5.4 3.9 1.7 0.4
7 4.6 3.4 1.4 0.3
8 5.0 3.4 1.5 0.2
9 4.4 2.9 1.4 0.2
10 4.9 3.1 1.5 0.1
Here, for illustration, I'm using the iris dataset and filtering out factors.
You could use Filter to select columns which are not integer.
Filter(Negate(is.integer), mtcars)
#Or explicitly mentioning non-integers
#Filter(function(x) !is.integer(x), mtcars)
In dplyr, we can use select_if
library(dplyr)
mtcars %>% select_if(Negate(is.integer))
#mtcars %>% select_if(~!is.integer(.))
To select those columns that appear as "integer" (according to your comment) you could select columns where all as.integer values correspond to the original ones using sapply.
mtcars[sapply(mtcars, function(i) all(as.integer(i) - i == 0))]
# cyl hp vs am gear carb
# Mazda RX4 6 110 0 1 4 4
# Mazda RX4 Wag 6 110 0 1 4 4
# Datsun 710 4 93 1 1 4 1
# Hornet 4 Drive 6 110 1 0 3 1
# Hornet Sportabout 8 175 0 0 3 2
# Valiant 6 105 1 0 3 1
# Duster 360 8 245 0 0 3 4
# Merc 240D 4 62 1 0 4 2
# Merc 230 4 95 1 0 4 2
# Merc 280 6 123 1 0 4 4
# Merc 280C 6 123 1 0 4 4
# Merc 450SE 8 180 0 0 3 3
# Merc 450SL 8 180 0 0 3 3
# Merc 450SLC 8 180 0 0 3 3
# Cadillac Fleetwood 8 205 0 0 3 4
# Lincoln Continental 8 215 0 0 3 4
# Chrysler Imperial 8 230 0 0 3 4
# Fiat 128 4 66 1 1 4 1
# Honda Civic 4 52 1 1 4 2
# Toyota Corolla 4 65 1 1 4 1
# Toyota Corona 4 97 1 0 3 1
# Dodge Challenger 8 150 0 0 3 2
# AMC Javelin 8 150 0 0 3 2
# Camaro Z28 8 245 0 0 3 4
# Pontiac Firebird 8 175 0 0 3 2
# Fiat X1-9 4 66 1 1 4 1
# Porsche 914-2 4 91 0 1 5 2
# Lotus Europa 4 113 1 1 5 2
# Ford Pantera L 8 264 0 1 5 4
# Ferrari Dino 6 175 0 1 5 6
# Maserati Bora 8 335 0 1 5 8
# Volvo 142E 4 109 1 1 4 2
If the which is mandatory you could built it in like so:
mtcars[which(sapply(mtcars, function(i) all(as.integer(i) - i == 0)))]
We can use negate from purrr
library(purrr)
library(dplyr)
mtcars %>%
select_if(negate(is.integer))
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