Update 2017-08-03
After writing this, Hadley changed some stuff again. The functions that used to be in purrr are now in a new mixed package called purrrlyr, described as:
purrrlyr contains some functions that lie at the intersection of purrr and dplyr. They have been removed from purrr in order to make the package lighter and because they have been replaced by other solutions in the tidyverse.
So, you will need to install + load that package to make the code below work.
Original post
Hadley frequently changes his mind about what we should use, but I think we are supposed to switch to the functions in purrr to get the by row functionality. At least, they offer the same functionality and have almost the same interface as adply from plyr.
There are two related functions, by_row and invoke_rows. My understanding is that you use by_row when you want to loop over rows and add the results to the data.frame. invoke_rows is used when you loop over rows of a data.frame and pass each col as an argument to a function. We will only use the first.
Examples
library(tidyverse)
iris %>%
by_row(..f = function(this_row) {
browser()
})
This lets us see the internals (so we can see what we are doing), which is the same as doing it with adply.
Called from: ..f(.d[[i]], ...)
Browse[1]> this_row
# A tibble: 1 × 5
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
<dbl> <dbl> <dbl> <dbl> <fctr>
1 5.1 3.5 1.4 0.2 setosa
Browse[1]> Q
By default, by_row adds a list column based on the output:
iris %>%
by_row(..f = function(this_row) {
this_row[1:4] %>% unlist %>% mean
})
gives:
# A tibble: 150 × 6
Sepal.Length Sepal.Width Petal.Length Petal.Width Species .out
<dbl> <dbl> <dbl> <dbl> <fctr> <list>
1 5.1 3.5 1.4 0.2 setosa <dbl [1]>
2 4.9 3.0 1.4 0.2 setosa <dbl [1]>
3 4.7 3.2 1.3 0.2 setosa <dbl [1]>
4 4.6 3.1 1.5 0.2 setosa <dbl [1]>
5 5.0 3.6 1.4 0.2 setosa <dbl [1]>
6 5.4 3.9 1.7 0.4 setosa <dbl [1]>
7 4.6 3.4 1.4 0.3 setosa <dbl [1]>
8 5.0 3.4 1.5 0.2 setosa <dbl [1]>
9 4.4 2.9 1.4 0.2 setosa <dbl [1]>
10 4.9 3.1 1.5 0.1 setosa <dbl [1]>
# ... with 140 more rows
if instead we return a data.frame, we get a list with data.frames:
iris %>%
by_row( ..f = function(this_row) {
data.frame(
new_col_mean = this_row[1:4] %>% unlist %>% mean,
new_col_median = this_row[1:4] %>% unlist %>% median
)
})
gives:
# A tibble: 150 × 6
Sepal.Length Sepal.Width Petal.Length Petal.Width Species .out
<dbl> <dbl> <dbl> <dbl> <fctr> <list>
1 5.1 3.5 1.4 0.2 setosa <data.frame [1 × 2]>
2 4.9 3.0 1.4 0.2 setosa <data.frame [1 × 2]>
3 4.7 3.2 1.3 0.2 setosa <data.frame [1 × 2]>
4 4.6 3.1 1.5 0.2 setosa <data.frame [1 × 2]>
5 5.0 3.6 1.4 0.2 setosa <data.frame [1 × 2]>
6 5.4 3.9 1.7 0.4 setosa <data.frame [1 × 2]>
7 4.6 3.4 1.4 0.3 setosa <data.frame [1 × 2]>
8 5.0 3.4 1.5 0.2 setosa <data.frame [1 × 2]>
9 4.4 2.9 1.4 0.2 setosa <data.frame [1 × 2]>
10 4.9 3.1 1.5 0.1 setosa <data.frame [1 × 2]>
# ... with 140 more rows
How we add the output of the function is controlled by the .collate param. There's three options: list, rows, cols. When our output has length 1, it doesn't matter whether we use rows or cols.
iris %>%
by_row(.collate = "cols", ..f = function(this_row) {
this_row[1:4] %>% unlist %>% mean
})
iris %>%
by_row(.collate = "rows", ..f = function(this_row) {
this_row[1:4] %>% unlist %>% mean
})
both produce:
# A tibble: 150 × 6
Sepal.Length Sepal.Width Petal.Length Petal.Width Species .out
<dbl> <dbl> <dbl> <dbl> <fctr> <dbl>
1 5.1 3.5 1.4 0.2 setosa 2.550
2 4.9 3.0 1.4 0.2 setosa 2.375
3 4.7 3.2 1.3 0.2 setosa 2.350
4 4.6 3.1 1.5 0.2 setosa 2.350
5 5.0 3.6 1.4 0.2 setosa 2.550
6 5.4 3.9 1.7 0.4 setosa 2.850
7 4.6 3.4 1.4 0.3 setosa 2.425
8 5.0 3.4 1.5 0.2 setosa 2.525
9 4.4 2.9 1.4 0.2 setosa 2.225
10 4.9 3.1 1.5 0.1 setosa 2.400
# ... with 140 more rows
If we output a data.frame with 1 row, it matters only slightly which we use:
iris %>%
by_row(.collate = "cols", ..f = function(this_row) {
data.frame(
new_col_mean = this_row[1:4] %>% unlist %>% mean,
new_col_median = this_row[1:4] %>% unlist %>% median
)
})
iris %>%
by_row(.collate = "rows", ..f = function(this_row) {
data.frame(
new_col_mean = this_row[1:4] %>% unlist %>% mean,
new_col_median = this_row[1:4] %>% unlist %>% median
)
})
both give:
# A tibble: 150 × 8
Sepal.Length Sepal.Width Petal.Length Petal.Width Species .row new_col_mean new_col_median
<dbl> <dbl> <dbl> <dbl> <fctr> <int> <dbl> <dbl>
1 5.1 3.5 1.4 0.2 setosa 1 2.550 2.45
2 4.9 3.0 1.4 0.2 setosa 2 2.375 2.20
3 4.7 3.2 1.3 0.2 setosa 3 2.350 2.25
4 4.6 3.1 1.5 0.2 setosa 4 2.350 2.30
5 5.0 3.6 1.4 0.2 setosa 5 2.550 2.50
6 5.4 3.9 1.7 0.4 setosa 6 2.850 2.80
7 4.6 3.4 1.4 0.3 setosa 7 2.425 2.40
8 5.0 3.4 1.5 0.2 setosa 8 2.525 2.45
9 4.4 2.9 1.4 0.2 setosa 9 2.225 2.15
10 4.9 3.1 1.5 0.1 setosa 10 2.400 2.30
# ... with 140 more rows
except that the second has the column called .row and the first does not.
Finally, if our output is longer than length 1 either as a vector or as a data.frame with rows, then it matters whether we use rows or cols for .collate:
mtcars[1:2] %>% by_row(function(x) 1:5)
mtcars[1:2] %>% by_row(function(x) 1:5, .collate = "rows")
mtcars[1:2] %>% by_row(function(x) 1:5, .collate = "cols")
produces, respectively:
# A tibble: 32 × 3
mpg cyl .out
<dbl> <dbl> <list>
1 21.0 6 <int [5]>
2 21.0 6 <int [5]>
3 22.8 4 <int [5]>
4 21.4 6 <int [5]>
5 18.7 8 <int [5]>
6 18.1 6 <int [5]>
7 14.3 8 <int [5]>
8 24.4 4 <int [5]>
9 22.8 4 <int [5]>
10 19.2 6 <int [5]>
# ... with 22 more rows
# A tibble: 160 × 4
mpg cyl .row .out
<dbl> <dbl> <int> <int>
1 21 6 1 1
2 21 6 1 2
3 21 6 1 3
4 21 6 1 4
5 21 6 1 5
6 21 6 2 1
7 21 6 2 2
8 21 6 2 3
9 21 6 2 4
10 21 6 2 5
# ... with 150 more rows
# A tibble: 32 × 7
mpg cyl .out1 .out2 .out3 .out4 .out5
<dbl> <dbl> <int> <int> <int> <int> <int>
1 21.0 6 1 2 3 4 5
2 21.0 6 1 2 3 4 5
3 22.8 4 1 2 3 4 5
4 21.4 6 1 2 3 4 5
5 18.7 8 1 2 3 4 5
6 18.1 6 1 2 3 4 5
7 14.3 8 1 2 3 4 5
8 24.4 4 1 2 3 4 5
9 22.8 4 1 2 3 4 5
10 19.2 6 1 2 3 4 5
# ... with 22 more rows
So, bottom line. If you want the adply(.margins = 1, ...) functionality, you can use by_row.
mdplyin dplyr, and hadley suggested that they might be brewing something based ondo. I guess it would also work here. – Gilmagilmanrowwise()which would group by each individual row – Unbreathedadplywhen you don't use a grouping though? as its closely integrated function is calledgroup_byNOTsplit_by– Zamora