Basic fSquared function for effect size of iv on dv (#123)

Author: soumyaray

R/evaluate_effects.R

@@ -0,0 +1,55 @@
+#' seminr fSquared Function
+#'
+#' The \code{fSquared} function calculates f^2 effect size for a given IV and DV
+#'
+#' @param seminr_model A \code{seminr_model} containing the estimated seminr model.
+#' @param iv An independent variable in the model.
+#' @param dv A dependent variable in the model.
+#'
+#' @usage
+#' fsquared(model, iv, dv)
+#'
+#' @references Cohen, J. (2013). Statistical power analysis for the behavioral sciences. Routledge.
+#'
+#' @examples
+#' mobi_mm <- constructs(
+#'              reflective("Image",        multi_items("IMAG", 1:5)),
+#'              reflective("Expectation",  multi_items("CUEX", 1:3)),
+#'              reflective("Quality",      multi_items("PERQ", 1:7)),
+#'              reflective("Value",        multi_items("PERV", 1:2)),
+#'              reflective("Satisfaction", multi_items("CUSA", 1:3)),
+#'              reflective("Complaints",   single_item("CUSCO")),
+#'              reflective("Loyalty",      multi_items("CUSL", 1:3))
+#'            )
+#'
+#' mobi_sm <- relationships(
+#'   paths(from = "Image",        to = c("Expectation", "Satisfaction", "Loyalty")),
+#'   paths(from = "Expectation",  to = c("Quality", "Value", "Satisfaction")),
+#'   paths(from = "Quality",      to = c("Value", "Satisfaction")),
+#'   paths(from = "Value",        to = c("Satisfaction")),
+#'   paths(from = "Satisfaction", to = c("Complaints", "Loyalty")),
+#'   paths(from = "Complaints",   to = "Loyalty")
+#' )
+#'
+#' mobi_pls <- estimate_pls(data = mobi,
+#'                          measurement_model = mobi_mm,
+#'                          structural_model = mobi_sm)
+#'
+#' fSquared(mobi_pls, "Image", "Satisfaction")
+#' @export
+# fSquared as per Cohen (2013)
+
+fSquared <- function(seminr_model, iv, dv) {
+  with_sm <- seminr_model$smMatrix
+  without_sm <- subset(with_sm, !((with_sm[, "source"] == iv) & (with_sm[, "target"] == dv)))
+  capture.output(
+    without_pls <- estimate_pls(data = seminr_model$data,
+                                measurement_model = seminr_model$mmMatrix,
+                                structural_model = without_sm)
+  )
+
+  with_r2 <- seminr_model$rSquared["Rsq", dv]
+  without_r2 <- without_pls$rSquared["Rsq", dv]
+
+  (with_r2 - without_r2) / (1 - with_r2)
+}