renamed res_ij to resi

R/resi.R

@@ -0,0 +1,37 @@
+## File Name: resi.R
+## File version: 1.0
+
+#' Compute rasch person-item residuals
+#'
+#' This function computes person-item residuals for rasch family adjacent-categories models
+#' like the Rasch model or the PCM
+#'
+#' @param thetahat_i Person parameter estimate for person i
+#' @param delta_hat_j Item threshold parameter estimates for item j
+#' @param res Response of person i to item j
+#' @param beta Estimated latent mean difference between groups, can be ignored
+#' @return A single scalar equal to the residual for person i on item j
+#' @import vcrpart
+#' @export
+
+resi <- function(thetahat_i,delta_hat_j,res,beta=0){
+  var=0
+  denomin=1
+  for (i in 1:length(delta_hat_j)) {
+
+    denomin=denomin+exp(i*(thetahat_i+beta)-sum(delta_hat_j[1:i]))
+  }
+  posterior=c(1)
+  for (i in 1:length(delta_hat_j)) {
+    posterior=c(posterior,exp(i*(thetahat_i+beta)-sum(delta_hat_j[1:i])))
+  }
+
+  posterior=posterior/denomin
+
+  for(i in 0:length(delta_hat_j)){
+
+    var=var+((i-sum(posterior*0:length(delta_hat_j)))**2)*posterior[i+1]
+  }
+  return((res-sum(posterior*0:length(delta_hat_j)))/sqrt(var))
+
+}