MAGMA_exact {MAGMA.R}

MAGMA_exact

Description

This function conducts exact many group matching for 2 to 4 groups. Exact means that only cases with the same value on the exact variable can be matched. It augments the original data set by relevant 'MAGMA.R' variables. For details, see below.

Usage

MAGMA_exact(Data, group, dist, exact, cores = 1, verbose = TRUE)

Arguments

Data

A data frame or tibble containing at least your grouping and distance variable. Data needs to be specified in your environment.

group

A character specifying the name of your grouping variable in the data. Note that MAGMA can only match your data for a maximum of 4 groups. Matching over two grouping variables (e.g., 2x2 Design) is possible by specifying group as a character vector with a length of two. In this case, each or the 2 grouping variables can only have two levels.

dist

A character specifying the name of your distance variable in data.

exact

A character specifying the name of the exact variable. Only cases with the same value on this variable can be matched.

cores

An integer defining the number of cores used for parallel computation.

verbose

TRUE or FALSE indicating whether matching information should be printed to the console.

Details

This function conducts nearest neighbor exact many group matching. It is applicable for two to four groups or a 2x2 design. As output, this function augments your original data by the variables weight, step, distance, and ID. Weight indicates whether a case was matched. Step specifies the iteration in which a case was matched. It also shows which cases were matched together. Distance indicates the mean difference within a match. Since matches with a lower distance are matched in an earlier iteration, step and distance are strongly correlated. Exact matching means that only cases with the same value on the exact variable can be matched. As example, only person of the same gender, the same school, or the same organization are possible matches. For standard matching, see MAGMA

Value

Your input data frame of valid cases augmented with matching relevant variables, namely weight, step, distance, and ID. In case of missing values on the distance or group variable, MAGMA_exact excludes them for the matching process. The returned data set does not contain those excluded cases. For more information, see Details.

Author(s)

Julian Urban

Examples

# Running this code will take a while
# Two-group exact matching using the data set 'MAGMA_sim_data'
# Matching variable 'gifted_support' (received giftedness support yes or no)
# 'MAGMA_sim_data_gifted_exact' contains the result of the matching
# Exact matching for 'enrichment' (participated in enrichment or not)
# Students that participated can only be matched with other
# students that participated and vice versa
MAGMA_sim_data_gifted_exact <- MAGMA_exact(Data = MAGMA_sim_data[c(1:80 ), ],
                                           group = "gifted_support",
                                           dist = "ps_gifted",
                                           exact = "enrichment",
                                           cores = 1)
head(MAGMA_sim_data_gifted_exact)


# Conducting three-group matching using the data set 'MAGMA_sim_data'
# Matching variable 'teacher_ability_rating' (ability rated from teacher as
# below average, average, or above average)
# 'MAGMA_sim_data_tar_exact' contains the result of the matching
# Exact matching for gender (male or female)
# Male students can only be matched to male students, female students can only
# be matched to female students
# Cores per default = 1
MAGMA_sim_data_tar_exact<- MAGMA_exact(Data = MAGMA_sim_data,
                                       group = "teacher_ability_rating",
                                       dist = "ps_tar",
                                       exact = "gender")
head(MAGMA_sim_data_tar_exact)

# 2x2 matching using the data set 'MAGMA_sim_data'
# Matching variables are 'gifted_support' (received giftedness support yes
# or no) and 'enrichment' (participated in enrichment or not)
# 'MAGMA_sim_data_gift_enrich_exact' contains the result of the matching
# 2x2 matching is equal to four-group matching
# Exact matching for for teacher rated ability (ability rated from teacher as
# below average, average, or above average)
# Below average students can only be matched to other below average rated
# students, average rated students can be matched with other average rated
# students, and above average rated students can only be matched to other
# above average rated students
MAGMA_sim_data_gift_enrich_exact <- MAGMA_exact(Data = MAGMA_sim_data,
                                                group = c("gifted_support", "enrichment"),
                                                dist = "ps_2x2",
                                                exact = "teacher_ability_rating",
                                                cores = 2)
head(MAGMA_sim_data_gift_enrich_exact)