R/conversions.R

In Swarchal/TCCS: Theta Comparative Cell Scoring

#' Convert cosine similarity to angular similarity
#'
#' If a cosine similarity has been calculated by cos_sim, then this function
#' will convert the value to angular similarity. Angular similarity is bound
#' between 0 and 1, with 1 being most similar, 0 being dissimilar, 0.5 being
#' orthogonal
#'
#' @param x vector of cosine similarity values
#' @return disim vector of angular similarity values
#'
#' @export
#'
#' @examples
#' vals <- runif(100, -1, 1) # random values
#' cossim_to_angsim(vals)

cossim_to_angsim <- function(x){

    # check range of values, give warning if outside
    # possible cosine similarity values
    range_x <- range(x, na.rm = TRUE)
    if (range_x[1] < -1 || range_x[2] > 1){
        warning("The input values are outside the expected range of -1 to 1")
    }

    disim <- 1 - acos(x) / pi
    return(disim)
}


#' Convert angular similarity to cosine similarity
#'
#' If an angular similarity has been calculated, then this will convery it to
#' cosine similarities. A cosine similarity is bound between -1 and 1, with
#' 1 being similar and -1 being similar, 0 being orthogonal.
#'
#' @param x vector of angular similarities
#' @return similarity vector of cosine similarities
#'
#' @export
#'
#' @examples
#' vals <- runif(100) # 100 values between 0 and 1
#' angsim_to_cossim(vals)

angsim_to_cossim <- function(x){

    # check range of values, should be between 0 and 1
    # return warning if outside those values
    range_x <- range(x, na.rm = TRUE)
    if (range_x[1] < 0 || range_x[2] > 1){
        warning("The input values are outside the expected range of 0 to 1")
    }

    similarity <- - cos(x * pi)
    return(similarity)
}