7.8 Mapping over different arguments

map2 and pmap

varying just a single value

mu <- list(5, 10, -3)
mu %>% 
  map(rnorm, n = 5) %>% 
  str()
## List of 3
##  $ : num [1:5] 5.21 4.64 5.76 4.27 3.63
##  $ : num [1:5] 10.43 9.19 11.44 9.57 10.66
##  $ : num [1:5] -2.68 -3.78 -1.42 -2.36 -2.91

varying both mu and sigmna

sigma <- list(1, 5, 10)

map2(mu, sigma, rnorm, n = 5) %>% str()
## List of 3
##  $ : num [1:5] 5.28 5.68 5.09 2.01 5.28
##  $ : num [1:5] 8.16 10.93 12.91 17 6.36
##  $ : num [1:5] 10.025 0.358 7.385 6.207 4.209

variying across mu, sigma, and n

n <- list(1, 3, 5)

args <- list(mean = mu, sd = sigma, n = n)

pmap(args, rnorm) %>% str()
## List of 3
##  $ : num 3.96
##  $ : num [1:3] 9.55 13.12 5.23
##  $ : num [1:5] -8.43 2.81 4.68 1.64 -11.86

If your data is all the same length it can be stored in a dataframe. Or if you have a dataframe of values you are planning to “apply” over.

library(tibble)
params <- tribble(
  ~mean, ~sd, ~n,
    5,     1,  1,
   10,     5,  3,
   -3,    10,  5
)
params %>% 
  pmap(rnorm)
## [[1]]
## [1] 3.900219
## 
## [[2]]
## [1] 17.56354 11.28961 10.44220
## 
## [[3]]
## [1]  -4.208965 -14.943289   3.119969  -5.171398  -4.827567

Having a dataframe and using list columns, you can change the function an it’s arguments with invoke_map

f <- c("runif", "rnorm", "rpois")
param <- list(
  list(min = -1, max = 1), 
  list(sd = 5), 
  list(lambda = 10)
)

invoke_map(f, param, n = 5) %>% str()
## List of 3
##  $ : num [1:5] 0.649 0.185 0.589 0.538 0.836
##  $ : num [1:5] 5.46 -3.23 3.33 4.09 -2.8
##  $ : int [1:5] 12 17 13 13 6

library(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
sim <- tribble(
  ~f,      ~params,
  "runif", list(min = -1, max = 1),
  "rnorm", list(sd = 5),
  "rpois", list(lambda = 10)
)
sim_invoked <- sim %>% 
  mutate(sim = invoke_map(f, params, n = 10))

sim_invoked
## # A tibble: 3 x 3
##   f     params           sim       
##   <chr> <list>           <list>    
## 1 runif <named list [2]> <dbl [10]>
## 2 rnorm <named list [1]> <dbl [10]>
## 3 rpois <named list [1]> <int [10]>

sim_invoked$sim
## [[1]]
##  [1] -0.03082414 -0.49508312 -0.48062004  0.08403188  0.29975168 -0.32716174
##  [7] -0.87810051 -0.09737830  0.67751007  0.14927467
## 
## [[2]]
##  [1]  -1.881454   6.205581  -4.738676   8.839889   4.586639  -4.473877
##  [7]  -3.440830  -4.992420 -10.536207   4.287095
## 
## [[3]]
##  [1] 13  9 10  7  6 14  7 15 10  6