The assignment pipe (%<>%) is not found when installing only the tidyverse

[kbzsl]

According to the magrittr tidyverse page “The easiest way to get magrittr is to install the whole tidyverse”, but the assignment pipe (%<>%) is not found when installing only the tidyverse (1.2.1).

y = 10

library(tidyverse)
y %<>% log()
#> Error in y %<>% log(): could not find function "%<>%"
y
#> [1] 10

library(magrittr)
#> 
#> Attaching package: 'magrittr'
#> The following object is masked from 'package:purrr':
#> 
#>     set_names
#> The following object is masked from 'package:tidyr':
#> 
#>     extract
y %<>% log()
y
#> [1] 2.302585

[kbzsl]

This statement (“The easiest way to get magrittr is to install the whole tidyverse”) is misleading and non-consistent with other information from tidyverse.org.

[andresrcs]

It is not misleading if you are aware of the difference between "installing" and "loading" a package in R (they are not the same).

[kbzsl]

That’s true.

On the other hand, what is the explanation that the assignment pipe (%<>%) is working in some instances without loading the magrittr packages (just the tidyverse)? For example:

library(tidyverse)

exp(log10(100)) + 1 
#> [1] 8.389056

test_funct <- function(x){
  
  print(x)
  
  x %<>% 
    log10() %>% 
    exp()
  y = x + 1
}

print(test_funct(100))
#> [1] 100
#> [1] 8.389056

[andresrcs]

I'm not getting your point, tidyverse simply doesn't load magrittr (and the documentation doesn't says that it does), beacuse library(tidyverse) only loads the core tidyverse packages, what is the confusing part?

[kbzsl]

Please check the previous two examples and concentrate on that part when only the tidyverse is loaded.

In first example the %<>% pipe was not working. But in case of second example (test_funct()) the %<>% pipe is working.
What is the reason for the different behavior?

[kbzsl]

Here is the code:

library(tidyverse)

# 1 case, assignment pipe is not working

y = 10

y %<>% log()
#> Error in y %<>% log(): could not find function "%<>%"

print(y)
#> [1] 10

# 2 case, assignment pipe is  working

exp(log10(100)) + 1 
#> [1] 8.389056

test_funct <- function(x){
  
  print(x)
  
  x %<>% 
    log10() %>% 
    exp()
  y = x + 1
}

print(test_funct(100))
#> [1] 100
#> [1] 8.389056

[cderv]

You are right, %<>% is found when used in a pipe flow with %>%, even if magrittr is not directly loaded.

library(tidyverse)

y = 10

y %<>% log10() %>% exp()

y
#> [1] 2.718282

^{Created on 2019-06-23 by the reprex package (v0.3.0.9000)}

I am really not sure why. I would assume that when used in a pipe flow with %>%, the %<>% operator is parsed by %>% operator and understand how to deal with it.

When %<>% is used on its own, it requires to have magrittr loaded after a library(magrittr) because tidyverse are not reexporting %<>%

[kbzsl]

This inconsistent behavior of the pipe operators is contradicting the principle behind the tibbles (and in general the tidyverse): “The whole point of tidy data is to store variables in a consistent way…"

[mishabalyasin]

@cderv

When %<>% is used on its own, it requires to have magrittr loaded after a library(magrittr) because tidyverse are not reexporting %<>%

I think, you are right. Let's take a look at AST:

library(lobstr)
ast(y %<>% log10() %>% exp())
#> █─`%>%` 
#> ├─█─`%<>%` 
#> │ ├─y 
#> │ └─█─log10 
#> └─█─exp

^{Created on 2019-06-28 by the reprex package (v0.3.0)}

The way I understand this, when %<>% is called, magrittr namespace is found because %>% is present.

Without %>% AST looks like this:

library(lobstr)
ast(v1 %<>% log10)
#> █─`%<>%` 
#> ├─v1 
#> └─log10

^{Created on 2019-06-28 by the reprex package (v0.3.0)}

And namespace is not loaded most likely.

Just in case, using two non-exported functions from magrittr fails as well, so I would put my money on the fact that pipe is re-exported:

library(lobstr)
ast(v1 %<>% log10 %T>% print)
#> █─`%T>%` 
#> ├─█─`%<>%` 
#> │ ├─v1 
#> │ └─log10 
#> └─print
v1 %<>% log10 %T>% print
#> Error in v1 %<>% log10 %T>% print: could not find function "%T>%"

^{Created on 2019-06-28 by the reprex package (v0.3.0)}

EDIT: Actually, this example is more illuminating, I think:

library(tidyverse)
v1 %>% log10 %T>% print
#> Error in v1 %>% log10 %T>% print: could not find function "%T>%"

library(lobstr)
ast(v1 %>% log10 %T>% print)
#> █─`%T>%` 
#> ├─█─`%>%` 
#> │ ├─v1 
#> │ └─log10 
#> └─print

^{Created on 2019-06-28 by the reprex package (v0.3.0)}

This version fails because when %T>% is called there is no magrittr namespace to look at.

[cderv]

Only ˋ%>%ˋ is reexported. You need to load package magrittr for other operators.

[mishabalyasin]

@Yarnabrina

With pipes, I thought the functions are supposed to be evaluated from left to right

They are evaluated from left to right. That is why pipe is evaluated first, and tee-pipe after that. At the point when tee-pipe is evaluated, there is no magrittr namespace anymore on a search path and it fails. When pipe is evaluated second, tee pipe (or any other pipe from magrittr) are enclosed in pipe and therefore magrittr namespace is on the search path.

What we can learn from that is re-exported functions do not load namespace into memory or rather it persists only until pipe is evaluated and then goes away.