View source: R/dummy_extract.R
step_dummy_extract | R Documentation |
step_dummy_extract()
creates a specification of a recipe step that will
convert nominal data (e.g. characters or factors) into one or more integer
model terms for the extracted levels.
step_dummy_extract(
recipe,
...,
role = "predictor",
trained = FALSE,
sep = NULL,
pattern = NULL,
threshold = 0,
other = "other",
naming = dummy_extract_names,
levels = NULL,
sparse = "auto",
keep_original_cols = FALSE,
skip = FALSE,
id = rand_id("dummy_extract")
)
recipe |
A recipe object. The step will be added to the sequence of operations for this recipe. |
... |
One or more selector functions to choose variables for this step.
See |
role |
Not used by this step since no new variables are created. |
trained |
A logical to indicate if the quantities for preprocessing have been estimated. |
sep |
Character string containing a regular expression to use for
splitting. |
pattern |
Character string containing a regular expression used for
extraction. |
threshold |
A numeric value between 0 and 1, or an integer greater or
equal to one. If less than one, then factor levels with a rate of
occurrence in the training set below |
other |
A single character value for the other category, default to
|
naming |
A function that defines the naming convention for new dummy columns. See Details below. |
levels |
A list that contains the information needed to create dummy
variables for each variable contained in |
sparse |
A single string. Should the columns produced be sparse vectors.
Can take the values |
keep_original_cols |
A logical to keep the original variables in the
output. Defaults to |
skip |
A logical. Should the step be skipped when the recipe is baked by
|
id |
A character string that is unique to this step to identify it. |
step_dummy_extract()
will create a set of integer dummy variables from a
character variable by extracting individual strings by either splitting or
extracting then counting those to create count variables.
Note that threshold
works in a very specific way for this step. While it is
possible for one label to be present multiple times in the same row, it will
only be counted once when calculating the occurrences and frequencies.
This recipe step allows for flexible naming of the resulting
variables. For an unordered factor named x
, with levels "a"
and "b"
, the default naming convention would be to create a
new variable called x_b
. The naming format can be changed using
the naming
argument; the function dummy_names()
is the
default.
An updated version of recipe
with the new step added to the
sequence of any existing operations.
When you tidy()
this step, a tibble is returned with
columns terms
, columns
, and id
:
character, the selectors or variables selected
character, names of resulting columns
character, id of this step
The return value is ordered according to the frequency of columns
entries
in the training data set.
This step produces sparse columns if sparse = "yes"
is being set. The
default value "auto"
won't trigger production fo sparse columns if a recipe
is prep()
ed, but allows for a workflow to toggle to "yes"
or "no"
depending on whether the model supports sparse_data and if the model is
is expected to run faster with the data.
The mechanism for determining how much sparsity is produced isn't perfect,
and there will be times when you want to manually overwrite by setting
sparse = "yes"
or sparse = "no"
.
This step performs an unsupervised operation that can utilize case weights.
As a result, case weights are only used with frequency weights. For more
information, see the documentation in case_weights and the examples on
tidymodels.org
.
dummy_extract_names()
Other dummy variable and encoding steps:
step_bin2factor()
,
step_count()
,
step_date()
,
step_dummy()
,
step_dummy_multi_choice()
,
step_factor2string()
,
step_holiday()
,
step_indicate_na()
,
step_integer()
,
step_novel()
,
step_num2factor()
,
step_ordinalscore()
,
step_other()
,
step_regex()
,
step_relevel()
,
step_string2factor()
,
step_time()
,
step_unknown()
,
step_unorder()
data(tate_text, package = "modeldata")
dummies <- recipe(~ artist + medium, data = tate_text) %>%
step_dummy_extract(artist, medium, sep = ", ") %>%
prep()
dummy_data <- bake(dummies, new_data = NULL)
dummy_data %>%
select(starts_with("medium")) %>%
names() %>%
head()
# More detailed splitting
dummies_specific <- recipe(~medium, data = tate_text) %>%
step_dummy_extract(medium, sep = "(, )|( and )|( on )") %>%
prep()
dummy_data_specific <- bake(dummies_specific, new_data = NULL)
dummy_data_specific %>%
select(starts_with("medium")) %>%
names() %>%
head()
tidy(dummies, number = 1)
tidy(dummies_specific, number = 1)
# pattern argument can be useful to extract harder patterns
color_examples <- tibble(
colors = c(
"['red', 'blue']",
"['red', 'blue', 'white']",
"['blue', 'blue', 'blue']"
)
)
dummies_color <- recipe(~colors, data = color_examples) %>%
step_dummy_extract(colors, pattern = "(?<=')[^',]+(?=')") %>%
prep()
dummies_data_color <- dummies_color %>%
bake(new_data = NULL)
dummies_data_color
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