pred <- ddply(data.frame(x=c(5:65)*0.01), .(x), function(t) data.frame(x = t$x, y = c(5:85)*0.01) ) pred$enrichment <- predict(sigmoid, pred) max_pred <- max(pred$enrichment, d$enrichment) p <- ggplot(pred,aes(x,y))+geom_tile(aes(fill=enrichment))+scale_fill_gradient(low = "white", high = "steelblue",limits=c(0,max_pred)) p <- p + xlab("x") + ylab("y") p <- p + geom_point(data=d,aes(x=x, y=y, colour=enrichment),size=20) +scale_colour_gradient(low = "white", high = "steelblue",limits=c(0,max_pred)) print(p)