Comments (9)
A draft syntax is like
x %>>% (~ symbol)
x %>>% (~ f(.) ~ symbol)
x %>>% (~ x ~ f(x) ~ symbol)
It can be best described by Start with ~
for side effect and end with a symbol for assignment.
An example is
mtcars %>>%
subset(mpg <= mean(mpg)) %>>%
(~ smtcars) %>>%
(~ dim(.) ~ dim_mtcars) %>>%
subset(select = c(mpg, wt, qsec)) %>>%
lm(formula = mpg ~ .) %>>%
summary %>>%
(~ summ) %>>%
(coefficients)
Estimate Std. Error t value Pr(>|t|)
(Intercept) 17.0183914 5.1411954 3.310201 0.0047583237
wt -2.9781345 0.6044032 -4.927397 0.0001823504
qsec 0.6033051 0.3053237 1.975953 0.0668509086
Inspect the environment after evaluating the code above.
> ls.str()
dim_mtcars : int [1:2] 18 11
smtcars : 'data.frame': 18 obs. of 11 variables:
$ mpg : num 18.7 18.1 14.3 19.2 17.8 16.4 17.3 15.2 10.4 10.4 ...
$ cyl : num 8 6 8 6 6 8 8 8 8 8 ...
$ disp: num 360 225 360 168 168 ...
$ hp : num 175 105 245 123 123 180 180 180 205 215 ...
$ drat: num 3.15 2.76 3.21 3.92 3.92 3.07 3.07 3.07 2.93 3 ...
$ wt : num 3.44 3.46 3.57 3.44 3.44 ...
$ qsec: num 17 20.2 15.8 18.3 18.9 ...
$ vs : num 0 1 0 1 1 0 0 0 0 0 ...
$ am : num 0 0 0 0 0 0 0 0 0 0 ...
$ gear: num 3 3 3 4 4 3 3 3 3 3 ...
$ carb: num 2 1 4 4 4 3 3 3 4 4 ...
summ : List of 11
$ call : language lm(formula = mpg ~ ., data = .)
$ terms :Classes 'terms', 'formula' length 3 mpg ~ wt + qsec
$ residuals : Named num [1:18] 1.658 -0.813 -1.643 1.386 -0.376 ...
$ coefficients : num [1:3, 1:4] 17.018 -2.978 0.603 5.141 0.604 ...
$ aliased : Named logi [1:3] FALSE FALSE FALSE
$ sigma : num 1.79
$ df : int [1:3] 3 15 3
$ r.squared : num 0.623
$ adj.r.squared: num 0.573
$ fstatistic : Named num [1:3] 12.4 2 15
$ cov.unscaled : num [1:3, 1:3] 8.217 -0.178 -0.437 -0.178 0.114 ...
from piper.
Given all syntax with (~ ...)
, operator ~
can be viewed in this context to be branching operator, which indicates that the following expression will be a side effect. It can either branch the left-hand side value to an expression (side-effect evaluation), or branch it to a symbol (assignment). After all, there's no point to evaluate a symbol for side effect (no side effect at all). Therefore this syntax seems not to create additional confusion or work at the expense of possible actions allowed in cases without this feature.
from piper.
Consider the =
syntax suggested by @yanlinlin82.
See #38.
from piper.
The following code adopts the =
syntax.
mtcars %>>%
subset(mpg <= mean(mpg)) %>>%
(~ smtcars) %>>% # side-effect assign
(~ dim_mtcars = dim(.)) %>>% # side-effect assign
subset(select = c(mpg, wt, qsec)) %>>%
lm(formula = mpg ~ .) %>>%
(sum_lm = summary(.)) %>>% # eval and assign
(coefficients)
from piper.
Definitely prefer this. I think this is much clearer, intuitive, and more readable.
from piper.
Think so too. Thanks @yanlinlin82 for the great suggestion. I'll implement it at branch feature/assign
soon and see how it works.
from piper.
The latest commit at feature/assign
uses symbolic call to perform the assignment, which allows the following usage:
> z <- list()
> 1:10 %>>% (~ z$a = length(.)) %>>% mean
[1] 5.5
> z
$a
[1] 10
That is, the assignment no longer calls assign()
but builds a symbolic call to perform the assignment, which does not require the expression on lhs of =
be a symbol and allows the usage like names(a) = ...
.
from piper.
That is more powerful!
from piper.
In v0.5, <-
and ->
will no longer be interpreted as lambda expression and are allowed to perform assignment in a pipeline, which makes the code even more readable in some cases.
from piper.
Related Issues (20)
- Handling incorrect usage of `.` (dot) HOT 17
- Support I() to avoid symbol clash HOT 1
- Does not support piping with lhs value unevaluated
- Consider class-based implementation of Pipe object HOT 1
- Preserve the visibility of output HOT 1
- Pipe's error HOT 2
- package?pipeR problem HOT 2
- Support operator-free pipeline HOT 2
- cat() string in pipeline HOT 1
- Add support of question mark as binary operator HOT 5
- Consider supporting question mark as ternary operator HOT 1
- Support global assignment
- not compatible with assign function HOT 6
- Pipe() HOT 2
- Have you thought of creating a pipeR version %<>>% of magrittr %<>%? HOT 2
- Leaked variable HOT 1
- Interfacing with data.tree
- use apply()
- debug(%>>%) for a pipe
- mouse support
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