-    ## px <- mean(x)
-    ## accuracy_imbalance_ratio <- (prediction_accuracy + accuracy_imbalance_difference/2) / (prediction_accuracy - accuracy_imbalance_difference/2)
-
-    ## # this works because of conditional probability
-    ## accuracy_x0 <- prediction_accuracy / (px*(accuracy_imbalance_ratio) + (1-px))
-    ## accuracy_x1 <- accuracy_imbalance_ratio * accuracy_x0
-
-    ## x0 <- df[x==0]$x
-    ## x1 <- df[x==1]$x
-    ## nx1 <- nrow(df[x==1])
-    ## nx0 <- nrow(df[x==0])
-
-    ## yx0 <- df[x==0]$y
-    ## yx1 <- df[x==1]$y 
- 
-    # tranform yz0.1 into a logistic distribution with mean accuracy_z0
-    ## acc.x0 <- plogis(0.5*scale(yx0) + qlogis(accuracy_x0))
-    ## acc.x1 <- plogis(1.5*scale(yx1) + qlogis(accuracy_x1))
-
-    ## w0x0 <- (1-x0)**2 + (-1)**(1-x0) * acc.x0
-    ## w0x1 <- (1-x1)**2 + (-1)**(1-x1) * acc.x1
-    pz <- mean(z)
-    accuracy_imbalance_ratio <- (prediction_accuracy + accuracy_imbalance_difference/2) / (prediction_accuracy - accuracy_imbalance_difference/2)
-
-    # this works because of conditional probability
-    accuracy_z0 <- prediction_accuracy / (pz*(accuracy_imbalance_ratio) + (1-pz))
-    accuracy_z1 <- accuracy_imbalance_ratio * accuracy_z0
-
-    z0x0 <- df[(z==0) & (x==0)]$x
-    z0x1 <- df[(z==0) & (x==1)]$x
-    z1x0 <- df[(z==1) & (x==0)]$x
-    z1x1 <- df[(z==1) & (x==1)]$x
-
-    yz0x0 <- df[(z==0) & (x==0)]$y
-    yz0x1 <- df[(z==0) & (x==1)]$y
-    yz1x0 <- df[(z==1) & (x==0)]$y
-    yz1x1 <- df[(z==1) & (x==1)]$y
-
-    nz0x0 <- nrow(df[(z==0) & (x==0)])
-    nz0x1 <- nrow(df[(z==0) & (x==1)])
-    nz1x0 <- nrow(df[(z==1) & (x==0)])
-    nz1x1 <- nrow(df[(z==1) & (x==1)])
-
-    yz1 <- df[z==1]$y 
-    yz1 <- df[z==1]$y 
-
-    # tranform yz0.1 into a logistic distribution with mean accuracy_z0
-    acc.z0x0 <- plogis(0.5*scale(yz0x0) + qlogis(accuracy_z0))
-    acc.z0x1 <- plogis(0.5*scale(yz0x1) + qlogis(accuracy_z0))
-    acc.z1x0 <- plogis(1.5*scale(yz1x0) + qlogis(accuracy_z1))
-    acc.z1x1 <- plogis(1.5*scale(yz1x1) + qlogis(accuracy_z1))
-
-    w0z0x0 <- (1-z0x0)**2 + (-1)**(1-z0x0) * acc.z0x0
-    w0z0x1 <- (1-z0x1)**2 + (-1)**(1-z0x1) * acc.z0x1
-    w0z1x0 <- (1-z1x0)**2 + (-1)**(1-z1x0) * acc.z1x0
-    w0z1x1 <- (1-z1x1)**2 + (-1)**(1-z1x1) * acc.z1x1
-
-    ##perrorz0 <- w0z0*(pyz0)
-    ##perrorz1 <- w0z1*(pyz1)
-
-    w0z0x0.noisy.odds <- rlogis(nz0x0,qlogis(w0z0x0))
-    w0z0x1.noisy.odds <- rlogis(nz0x1,qlogis(w0z0x1))
-    w0z1x0.noisy.odds <- rlogis(nz1x0,qlogis(w0z1x0))
-    w0z1x1.noisy.odds <- rlogis(nz1x1,qlogis(w0z1x1))
-
-    df[(z==0)&(x==0),w:=plogis(w0z0x0.noisy.odds)]
-    df[(z==0)&(x==1),w:=plogis(w0z0x1.noisy.odds)]    
-    df[(z==1)&(x==0),w:=plogis(w0z1x0.noisy.odds)]    
-    df[(z==1)&(x==1),w:=plogis(w0z1x1.noisy.odds)]    
-
-    df[,w_pred:=as.integer(w > 0.5)]
+    ## probablity of an error is correlated with y
+    p.correct <- plogis(y_bias*scale(y) + qlogis(prediction_accuracy))
+
+    acc.x0 <- p.correct[df[,x==0]]
+    acc.x1 <- p.correct[df[,x==1]]
+
+    df[x==0,w:=rlogis(.N,qlogis(1-acc.x0))]
+    df[x==1,w:=rlogis(.N,qlogis(acc.x1))]
+
+    df[,w_pred := as.integer(w>0.5)]
+