Question

In a plot(x,y) is there any way to plot a line/curve/function that would split **at every x (see DWins comment) ** the observations in 2 halfs? So that **at arround every x (see DWins comment) ** the same number of observations are above and below this line/curve/function? Is there any way to get the (x,y) coordinates or the function of this line/curve/function?

As regressing the data is problematic due to outliers/non-normality etc etc, i though a programming method might provide a viable solution without resorting to complicated regression methods.

Thanks a lot

Answer 1

First generate some test data:

x <- c(1, 1, 1, 2, 2, 3, 3, 3, 3)
y <- seq_along(x)

Now assuming the data is sorted by x calculate the median at each x and plot:

plot(y ~ x)

m <- tapply(y, x, median)
lines(m ~ unique(x))