attr_getter() no longer uses partial matching. For example, if an
x object has a
labels attribute but no
attr_getter("label")(x) will no longer extract the
labels attribute (#460, @huftis).
modify_at() now preserve the class of atomic vectors instead of promoting them to lists. New S3 methods are provided for character, logical, double, and integer classes (@t-kalinowski, #417).
We noticed the following issues during reverse dependencies checks:
reduce() fails with this message:
Error: `.x` is empty, and no `.init` supplied, this is because
reduce() now returns
.x is empty. Fix the problem by supplying an appropriate argument to
.init, or by providing special behaviour when
.x has length 0.
The type predicates have been migrated to rlang. Consequently the
bare-type-predicates documentation topic is no longer in purrr, which might cause a warning if you cross-reference it.
purrr no longer depends on lazyeval or Rcpp (or dplyr, as of the previous version). This makes the dependency graph of the tidyverse simpler, and makes purrr more suitable as a dependency of lower-level packages.
There have also been two changes to eliminate name conflicts between purrr and dplyr:
The plucking mechanism used for indexing into data structures with
map() has been extracted into the function
pluck(). Plucking is often more readable to extract an element buried in a deep data structure. Compare this syntax-heavy extraction which reads non-linearly:
to the equivalent pluck:
x %>% pluck(1, accessor, "foo")
as_function() is now
as_mapper() because it is a tranformation that makes sense primarily for mapping functions, not in general (#298).
.null has been renamed to
.default to better reflect its intent (#298).
.default is returned whenever an element is absent or empty (#231, #254).
as_mapper() sanitises primitive functions by transforming them to closures with standardised argument names (using
rlang::as_closure()). For instance
+ is transformed to
function(.x, .y) .x + .y. This results in proper argument matching so that
, .x = 5)) produces
list(5 - 1, 5 - 2, ...).
The argument list for formula-functions has been tweaked so that you can refer to arguments by position with
..2, and so on. This makes it possible to use the formula shorthand for functions with more than two arguments (#289).
All map functions now treat
NULL the same way as an empty vector (#199), and return an empty vector if any input is an empty vector.
The data frame suffix
_df has been (soft) deprecated in favour of
_dfr to more clearly indicate that it’s a row-bind. All variants now also have a
_dfc for column binding (#167). (These will not be terribly useful until
dplyr::bind_cols() have better semantics for vectors.)
The modify functions are S3 generics. However their default methods should be sufficient for most classes since they rely on the semantics of
modify.default() is thus a shorthand for
x <- map(x, f).
The legacy function
update_list() is basically a version of
list_modify that evaluates formulas within the list. It is likely to be deprecated in the future in favour of a tidyeval interface such as a list method for
Thanks to @dchiu911, the unit test coverage of purrr is now much greater.
All predicate functions are re-exported from rlang (#124).
cross_n() has been renamed to
_n suffix was removed for consistency with
pmap() (originally called
map_n() at the start of the project) and
transpose() (originally called
cross_d() has been renamed to
cross_df() for consistency with
reduce() now throws an error if
.x is empty and
.init is not supplied.
zip_n() have been removed.
set_names() can now take a function to tranform the names programmatically (#276), and you can supply names in
... to reduce typing even more more (#316).
set_names() is now powered by
This is a compatibility release with dplyr 0.6.0.
unslice()have been moved to purrrlyr. This is a bit of an aggresive change but it allows us to make the dependencies much lighter.
as_function() gains a
.null argument that for character and numeric values allows you to specify what to return for null/absent elements (#110). This can be used with any map function, e.g.
map_int(x, 1, .null = NA)
as_function() is now generic.
is_function() that returns
TRUE only for regular functions.
Fix crash on GCC triggered by
There are two handy infix functions:
accumulate() has been added to handle recursive folding. It is shortand for
Reduce(f, .x, accumulate = TRUE) and follows a similar syntax to
reduce() (#145). A right-hand version
accumulate_right() was also added.
invoke() has been overhauled to be more useful: it now works similarly to
.x is NULL, and hence
map_call() has been deprecated.
invoke_map() is a vectorised complement to
invoke() (#125), and comes with typed variants
zip_n() (#128). The name more clearly reflects the intent (transposing the first and second levels of list). It no longer has fields argument or the
.simplify argument; instead use the new
possibly() are experimental functions for working with functions with side-effects (e.g. printed output, messages, warnings, and errors) (#120).
safely() is a version of
try() that modifies a function (rather than an expression), and always returns a list with two components,
is_null() is the snake-case version of
We are still figuring out what belongs in dplyr and what belongs in purrr. Expect much experimentation and many changes with these functions.
map() now always returns a list. Data frame support has been moved to
dmap(). The latter supports sliced data frames as a shortcut for the combination of
x %>% by_slice(dmap, fun, .collate = "rows"). The conditional variants
dmap_if() also support sliced data frames and will recycle scalar results to the slice size.
map_rows() has been renamed to
invoke_rows(). As other rows-based functionals, it collates results inside lists by default, but with column collation this function is equivalent to
The rows-based functionals gain a
.to option to name the output column as well as a
.collate argument. The latter allows to collate the output in lists (by default), on columns or on rows. This makes these functions more flexible and more predictable.
map*() now use custom C code, rather than relying on
mapply() etc. The performance characteristcs are very similar, but it allows us greater control over the output (#118).