使用不纯的 function 遍历数据帧的行的最优雅的方法是什么？

Question

If I have the following piece of code:

my_func <- function(var1, var2, var3, var4) {
    ... (side effect included) 
}

df <- crossing(
    nesting(var1=...,var2=....)
    nesting(var3=...,var4=....)
)

What is the most elegant way to apply my_func over every single row of df? Plus my_func is not a pure function, it is designed to carry out some side effects (IO, plot...)

Method 1

my_func_wrapper <- function(row) {
  my_func(row['var1'], row['var2'], row['var3'], row['var4'])
}

# Vector coercion is a problem, if variables are not the same type.
apply(df, 1, my_func_wrapper)

Method 2

df %>%
  rowwise() %>%
  do(result=invoke(my_func, .)) %>% #If it ends here, I will be pretty happy.
  .$result # Relying auto print feature to plot or trigger some side effect

Method 3

#This looks pretty good on its own but it does not play well with the pipe %>%
foreach(row=iter(df, by='row'))  %do% invoke(my_func, row)

#Method 3.1 (With Pipe)
 df %>%
   (function(df) foreach(row=iter(df, by='row'))  %do% invoke(my_func, row))

#Method 3.2 this does not work
# df %>%
#   foreach(row=iter(., by='row'))  %do% invoke(my_func, row)

#Method 3.3 this does not work
#I am trying to get this work with purrr's simplified anonymous function, but it does not work.
# df %>%
#    as_function(~ foreach(row=iter(., by='row'))  %do% invoke(my_func, row))

Is there a better way, which plays with %>% well, to do this?

Answer 1

Honestly, I'd use purr's pmap::pmap

library(tidyverse)

df = data.frame(
  x = rnorm(10),
  y = runif(10)
)
df %>% 
  pmap_dbl(function(x, y) {
    min(x,y)
  })

Answer 2

I find the tidyverse offers to be still worse than plyr for many of these kind of operations. Example:

> library(plyr)
> library(tidyverse)
> #dummy function
> your_function = function(...) {do.call(args = list(..., sep = " + "), what = str_c)}
> alply(mpg[1:5, ], .margins = 1, .fun = function(row) {
+   your_function(row$manufacturer, row$cyl, row$trans)
+ }) %>% unlist()
                      1                       2                       3                       4                       5 
  "audi + 4 + auto(l5)" "audi + 4 + manual(m5)" "audi + 4 + manual(m6)"   "audi + 4 + auto(av)"   "audi + 6 + auto(l5)" 

I don't know what you are trying to collect from the function, but probably you will want alply() or adply() .