declare_assignment: Declare assignment procedure

Description Usage Arguments Details Value Examples

Description

Declare assignment procedure

Usage

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declare_assignment(..., handler = assignment_handler, label = NULL)

assignment_handler(data, ..., assignment_variable = "Z",
  append_probabilities_matrix = FALSE)

Arguments

...

arguments to be captured, and later passed to the handler

handler

a tidy-in, tidy-out function

label

a string describing the step

data

A data.frame.

assignment_variable

Name for assignment variable (quoted). Defaults to "Z". Argument to be used with default handler.

append_probabilities_matrix

Should the condition probabilities matrix be appended to the data? Defaults to FALSE. Argument to be used with default handler.

Details

declare_assignment can work with any assignment_function that takes data and returns data. The default handler is conduct_ra from the randomizr package. This allows quick declaration of many assignment schemes that involve simple or complete random assignment with blocks and clusters. The arguments to conduct_ra can include N, block_var, clust_var, m, m_each, prob, prob_each, block_m, block_m_each, block_prob, block_prob_each, num_arms, and conditions. The arguments you need to specify are different for different designs. For details see the help files for complete_ra, block_ra, cluster_ra, or block_and_cluster_ra.

By default, declare_assignment declares a simple random assignment with probability 0.5.

Custom assignment handlers should augment the data frame with an appropriate column for the assignment(s).

Value

A function that takes a data.frame as an argument and returns a data.frame with additional columns appended including an assignment variable and (optionally) probabilities of assignment.

Examples

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# Default handler delegates to conduct_ra

# Declare assignment of m units to treatment
my_assignment <- declare_assignment(m = 50)

# Declare assignment specifying assignment probability for each block
my_assignment <- declare_assignment(block_prob = c(1/3, 2/3), blocks = female)

# Declare assignment of clusters with probability 1/4
my_assignment <- declare_assignment(
  prob = 1/4,
  clusters = classrooms,
  assignment_variable = "X1"
)
 
# Declare factorial assignment (Approach 1): 
#   Use complete random assignment to assign T1 and then use T1 as a block to assign T2. 
 design <- declare_population(N = 4) + 
   declare_assignment(assignment_variable = "T1") + 
   declare_assignment(blocks = T1, assignment_variable = "T2")
   draw_data(design)
   
# Declare factorial assignment (Approach 2): 
#   Assign to four conditions and then split into separate factors. 
 design <- declare_population(N = 4) + 
   declare_assignment(conditions = 1:4) + 
   declare_step(fabricate, T1 = as.numeric(Z %in% 2:3), T2 = as.numeric(Z %in% 3:4))
   draw_data(design)
   
# Declare assignment using custom handler

custom_assignment <- function(data, assignment_variable = "X") {
 data[, assignment_variable] <- rbinom(n = nrow(data),
                                       size = 1,
                                       prob = 0.5)
 data
 }
 
 declare_population(N = 6) + 
   declare_assignment(handler = custom_assignment, assignment_variable = "X")
   

graemeblair/DeclareDesign documentation built on Oct. 22, 2018, 3:50 a.m.