Custom function to loop over a list

Question

I have a working custom function but not sure how to allow it to loop with a list of inputs. Looks like I need to understand apply() and the such but I'm not quite there with my current setup. The function uses rollapply() to find the largest metric for a given time frame.

library(zoo)
library(dplyr)

# Data
set.seed(1)
df <- tibble(player = rep(LETTERS[1:2], each = 10),
             minute = rep(1:10, times = 2),
             tdc = sample(100:200,size = 20),
             sumad = sample(1:10, size = 20, replace = TRUE))

# Custom function
x_min_roll <- function(df, metric, n_minutes, fun){
  metric <- ensym(metric)
  newname <- glue::glue("{rlang::as_string(metric)}_x{as.character(n_minutes)}")
  df %>% 
    # dynamically create new column name based on input
    mutate("{newname}" := rollapply(!!metric, n_minutes, fun, align='left', fill=NA)) %>% 
    group_by(player) %>% 
    slice_max(.data[[newname]]) %>% 
    select(player, .data[[newname]])
}

# This works
df %>% 
  x_min_roll(metric = tdc, n_minutes = 2, fun = sum)

# A tibble: 2 x 2
# Groups:   player [2]
  player tdc_x2
  <chr>   <int>
1 A         339
2 B         380

I would like to be able to do this:

metric_list <- c('tdc', 'sumad')
minutes_list <- c(2,5)

df %>% 
  x_min_roll(metric = metric_list, n_minutes = minutes_list, fun = sum) %>% 
  # maybe a few more steps here.... to get this

# A tibble: 2 x 5
  player tdc_x2 tdc_x5 sumad_x2 sumad_x5
  <chr>   <dbl>  <dbl>    <dbl>    <dbl>
1 A         339    793       20       36
2 B         380    866       19       41

akrun · Accepted Answer · 2022-02-12 15:51:00Z

2

We can use map2 to loop over the corresponding elements of both vectors

library(purrr)
library(dplyr)
map2(metric_list, minutes_list, 
  ~ df %>%
    x_min_roll(metric = !!.x, n_minutes = .y, fun = sum))

-output

[[1]]
# A tibble: 2 × 2
# Groups:   player [2]
  player tdc_x2
  <chr>   <int>
1 A         339
2 B         380

[[2]]
# A tibble: 3 × 2
# Groups:   player [2]
  player sumad_x5
  <chr>     <int>
1 A            36
2 B            41
3 B            41

EDIT: Based on @Onyambu's comments

If we want for each combination, then use crossing to create the combination

library(tidyr)
crossing(metric_list, minutes_list) %>% 
 pmap(~ df %>% 
      x_min_roll(metric = !!.x, n_minutes = .y, fun = sum))

Based on the comments from the OP, if we want to combine the datasets

crossing(metric_list, minutes_list) %>% 
 pmap(~ df %>% x_min_roll(metric = !!.x, n_minutes = .y, fun = sum)) %>%
    reduce(inner_join, by = 'player')

edited Feb 12, 2022 at 15:51

answered Feb 11, 2022 at 16:44

akrun

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10 Comments

Onyambu Over a year ago

Since .y is numeric, I believe you could ignore the bang bang operator on it. in that case, the naming will be as required. Great solution

akrun Over a year ago

@Onyambu thanks, I overlooked that part.

seansteele Over a year ago

If I add another value the minutes list like this minutes_list <- c(2,3,5). I receive and error message Error: Mapped vectors must have consistent lengths: *.x has length 2 * .y has length 3

akrun Over a year ago

@seansteele then what about metric_list it is only of length 2. I am not sure what you are trying to do with that function when one of the input is of length greater different than the other

akrun Over a year ago

@seansteele your function is constructed in such a way to take a single value for metric and n_minutes (if I understand correctly)

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