R/common.R

In qdap: Bridging the Gap Between Qualitative Data and Quantitative Analysis

#' Find Common Words Between Groups
#' 
#' Find common words between grouping variables (e.g., people).
#' 
#' @param word.list A list of named character vectors.
#' @param overlap Minimum/exact amount of overlap.
#' @param equal.or A character vector of c(\code{"equal"}, \code{"greater"}, 
#' \code{"more"}, \code{"less"}).
#' @param \dots In lieu of \code{word.list} the user may input n number of 
#' character vectors.
#' @return Returns a dataframe of all words that match the criteria set by 
#' \code{overlap} and \code{equal.or}.
#' @export
## @examples
## a <- c("a", "cat", "dog", "the", "the")                                                              
## b <- c("corn", "a", "chicken", "the")                                                                
## d <- c("house", "feed", "a", "the", "chicken")                                                       
## common(a, b, d, overlap=2)  
## common(a, b, d, overlap=3)                                                                          
##                                                                                                      
## r <- list(a, b, d)  
## common(r)                                                                                 
## common(r, overlap=2)                                                                                            
##                                                                                                     
## common(word_list(DATA$state, DATA$person)$cwl, overlap = 2) 
common <-
function(word.list, overlap = "all", equal.or = "more", ...){
    overlap
    equal.or
    UseMethod("common")
}


#' list Method for common
#' 
#' @param word.list A list of names character vectors.
#' @param overlap Minimum/exact amount of overlap.
#' @param equal.or A character vector of c(\code{"equal"}, \code{"greater"}, 
#' \code{"more"}, \code{"less"}).
#' @param \dots In lieu of word.list the user may input n number of character 
#' vectors.
#' @export
#' @method common list
common.list <-
function(word.list, overlap = "all", equal.or = "more", ...){
    if(overlap=="all") {
        OL <- length(word.list) 
    } else {
        OL <- overlap
    }
    LIS <- sapply(word.list, unique)
    DF <- as.data.frame(table(unlist(LIS)), stringsAsFactors = FALSE)
    names(DF) <- c("word", "freq")
    DF <- DF[order(-DF$freq, DF$word), ]
    DF <- switch(equal.or,
        equal = DF[DF$freq == OL, ],
        greater = DF[DF$freq > (OL - 1), ],
        more = DF[DF$freq > (OL - 1), ],
        less = DF[DF$freq < (OL + 1), ])
    if (nrow(DF) == 0) {
        message(paste(overlap, "groups do not have any words in common."))
        return(invisible(NULL))
    }
    rownames(DF) <- 1:nrow(DF)
    return(DF)
}


#' @export
common.default <-
    function(..., overlap = "all", equal.or = "more", word.list){
        LIS <- list(...)
        return(common.list(LIS, overlap, equal.or))
}