library(ggplot2)

x.centers <- c(0, .14, -.164)
x.ses <- c(0.5, 0.2, 0.12)
y.centers <- c(0.01,.13, -.13)
y.ses <- c(0.05, 0.13, 0.24)

NN <- 1000#00
Sample1 <- cbind(rnorm(NN, x.centers[1], x.ses[1]), rnorm(NN, y.centers[1], y.ses[1]))
Sample2 <- cbind(rnorm(NN, x.centers[2], x.ses[2]), rnorm(NN, y.centers[2], y.ses[2]))
Sample3 <- cbind(rnorm(NN, x.centers[3], x.ses[3]), rnorm(NN, y.centers[3], y.ses[3]))

PlotFrame <- data.frame(cbind(rep(c("G1", "G2", "G3"), each = NN), rbind(Sample1, Sample2, Sample3)))
colnames(PlotFrame) <- c("LABELS", "X", "Y")
PlotFrame[, 2:3] <- apply(PlotFrame[, 2:3], 2, as.numeric)

Plot1 <- ggplot(data = PlotFrame, aes(x = X, y = Y, colour = LABELS))
Plot1 <- Plot1 + geom_density2d()
print(Plot1)

Plot2 <- ggplot(data = PlotFrame, aes(x = X, y = Y, group = LABELS))
Plot2 <- Plot2 + stat_density2d(aes(colour = ..level..), fill = "transparent", geom="polygon")
print(Plot2)

Plot3 <- ggplot(data = PlotFrame, aes(x = X, y = Y, group = LABELS))
Plot3 <- Plot3 + stat_density2d(aes(fill = LABELS, colour = LABELS, alpha = ..level..), geom="polygon")
print(Plot3)