Created difficulty matrix generation R script + initial scenarios

Scripts/R/generate_item_difficulties.R

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+###################################################
+# Function: generate_diff_irt
+# Generates item difficulty threshold matrix for
+# IRT model simulation
+###################################################
+
+
+generate_diff_irt <- function(J=7,M=4) {
+  # if J=7, item 5. Else, item 3
+  if(J==7){
+    i <- 5
+  }
+  if(J==4){
+    i <- 3
+  }
+  difficulties = matrix(c(0), J,M-1)
+  rownames(difficulties)=paste("item",1:J)
+  colnames(difficulties)=paste("Moda", 1:(M-1))
+  for (j in 1:J){
+    difficulties[j,1] = qnorm(j/(J+1))
+  }
+  for (j in 1:J){
+    for (m in 2:(M-1)){
+      difficulties[j,m]= difficulties[j,1]+(m-1)*2/(M-2)
+    }
+  }
+  difficulties = difficulties-mean(difficulties)
+  return(difficulties)
+}
+
+
+
+
+
+###################################################
+# GENERATE MATRIX FOR SIMULATION
+###################################################
+
+