# R/convert.d.to.nnc.R In userfriendlyscience: Quantitative Analysis Made Accessible

#### Documented in convert.d.to.nnc

#' Helper functions for Numbers Needed for Change
#'
#' These two functions are used by \code{\link{nnc}} to compute the Numbers
#' Needed for Change.
#'
#' These two functions are used by \code{\link{nnc}} to compute the Numbers
#' Needed for Change.
#'
#' @aliases convert.d.to.nnc convert.d.to.eer
#' @param d The value of Cohen's \emph{d}.
#' @param cer The Control Event Rate.
#' @param r The correlation between the determinant and behavior (for mediated
#' Numbers Needed for Change).
#' @param eventDesirable Whether an event is desirable or undesirable.
#' @param eventIfHigher Whether scores above or below the threshold are
#' considered 'an event'.
#' @return The converted value.
#' @author Gjalt-Jorn Peters & Stefan Gruijters
#'
#' Maintainer: Gjalt-Jorn Peters <gjalt-jorn@@userfriendlyscience.com>
#' @seealso \code{\link{nnc}}
#' @references Gruijters, S. L. K., & Peters, G.-J. Y. (2017). Introducing the
#' Numbers Needed for Change (NNC): A practical measure of effect size for
#' intervention research.
#' @keywords utilities
#' @examples
#'
#' convert.d.to.eer(d=.5, cer=.25);
#' convert.d.to.nnc(d=.5, cer=.25);
#'
#' @export convert.d.to.nnc
convert.d.to.nnc <- function(d, cer, r = 1, eventDesirable=TRUE, eventIfHigher=TRUE) {

### Based on http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0019070
### Consistent with http://rpsychologist.com/d3/cohend/

d <- convert.r.to.d(convert.d.to.r(d) * r);

if (is.null(cer)) {
# if (eventDesirable) {
#   return(1 / (2 * pnorm(d / sqrt(2)) - 1));
# } else {
cat0("Not implemented yet!");
# }
} else {
eer <- convert.d.to.eer(d, cer, eventDesirable=eventDesirable, eventIfHigher=eventIfHigher);
if (eventDesirable) {
nnc <- 1 / (eer - cer);
} else {
nnc <- 1 / (cer - eer);
}
}
attr(nnc, 'eer') <- eer;
return(nnc);
}


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userfriendlyscience documentation built on May 2, 2019, 1:09 p.m.