makeCaseWhenVariable {crunch}

Create a categorical or numeric variable based on conditions

Description

Conditions are specified using a series of formulas: the left-hand side is the condition that must be true (a CrunchLogicalExpr) and the right-hand side is where to get the value if the condition on the left-hand side is true. When creating a categorical variable, the right-hand side must be a Category or a categorical CrunchVariable or CrunchExpression, while for numeric variables it is a single number or variable or expression.

Usage

makeCaseWhenVariable(..., data = NULL, cases = NULL, name, type = NULL)

caseWhenExpr(..., data = NULL, cases = NULL, type = NULL)

Arguments

...

formulas where the left hand side is a CrunchLogicalExpression (or TRUE to indicate the "else" case that will be met if all the other expression are not met) and the right hand side is a CrunchVariable that should be filled in, a Category object describing the Category it should be used, a string which will be the name of the Category or NA to indicate that it should be replaced with the system missing value. For makeCaseWhenVariable() non-formula arguments will be passed to ⁠[VarDef()]⁠

data

A CrunchDataset to use if variable aliases are left bare in the formulas.

cases

A list of formulas that match the description in ... or a list of lists with named items, "expression" (like the left-hand side of the formulas above), "fill" for a variable to fill in, or "name", "id", and other items that describe a category.

name

For makeCaseWhenVariable() the name of the variable to create.

type

The type of the variable to output (either "categorical" or "numeric"), only required if all fills are expressions and so their type cannot be guessed automatically.

Value

makeCaseWhenVariable() returns a VariableDefinition and caseWhenExpr() returns an expression

Examples

## Not run: 
# Creating categorical variables
ds$new_var <- makeCaseWhenVariable(
   ds$x %in% c("a", "b") ~ ds$y, # can fill with a variable
   ds$x %in% c("c", "d") ~ Category(name = "c or d", numeric_value = 10), # or a Category
   # If none of the categories match, will be set to missing unless you
   # specify an "else" case with `TRUE` in the left hand side
   TRUE ~ Category(name = "catch all"),
   name = "combined x and y"
)

ds$brand_x_pref <- makeCaseWhenVariable(
   ds$brand[[1]] == "Brand X" ~ ds$pref[[1]],
   ds$brand[[2]] == "Brand X" ~ ds$pref[[2]],
   ds$brand[[3]] == "Brand X" ~ ds$pref[[3]],
   name = "brand x preference"
)

ds$x_among_aware <- makeCaseWhenVariable(
   ds$aware_x == "Yes" ~ ds$x,
   TRUE ~ Category(name = "(Not aware)", missing = TRUE),
   name = "x (among respondents aware of x)"
)

ds$new_num_var <- makeCaseWhenVariable(
  ds$x %in% c("a", "b") ~ ds$z, # LHS as before, RHS can be numeric variables,
  ds$x == "c" ~ ds$z * 10, # expressions,
  ds$x == "d" ~ 100, # or numbers
  name = "New numeric variable"
)

ds$capped_z <- makeCaseWhenVariable(
  ds$z > 10 ~ 10,
  TRUE ~ ds$z,
  name = "Capped z"
)

# caseWhenExpr can be used inside other expressions
ds$brand_x_prefer_high <- VarDef(
   selectCategories(
       caseWhenExpr(
           ds$brand_shown[[1]] == "Brand X" ~ ds$ratings[[1]],
           ds$brand_shown[[2]] == "Brand X" ~ ds$ratings[[2]],
           ds$brand_shown[[3]] == "Brand X" ~ ds$ratings[[3]]
       ),
       c("Best", "Very Good")
   ),
   name = "Rate X highly"
)

# Using lists in `cases` argument can be helpful when working programmatically
source_var <- ds$x
inclusion_condition <- ds$skipped_x != "Yes"

ds$x2_among_aware <- makeCaseWhenVariable(
   cases = list(list(fill = source_var, expression = inclusion_condition)),
   name = "x2 among aware"
)

## End(Not run)