RX LINQ partition the input stream

Question

I have a input stream where the input element consist of Date, Depth and Area. I want to plot the Area against the Depth and want therefor to take out a window of Depth e.g. between 1.0-100.0m. The problem is that I want to down sample the input stream since there can be many inputs with close Depth values. I want to partition the input into x bins, e.g. 2 bins means all depth values between 1-50 is averaged in the first bin and 51-100 in the second bin.

I was thinking something like this:

var q = from e in input
         where (e.Depth > 1) && (e.Depth <= 100)
         // here I need some way of partition the sequence into bins
         // and averaging the elements.

Split a collection into `n` parts with LINQ? wants to do something similar without rx.

Answer 1

Modified answer as per your comment. steps = number of buckets.

var min = 1, max = 100;
var steps = 10;
var f = (max - min + 1) / steps; // The extra 1 is really an epsilon. #hack
var q = from e in input
        where e.Depth > 1 && e.depth <= 100
        let x = e.Depth - min
        group e by x < max ? (x - (x % f)) : ;

This is the function we're grouping by for the given e.Depth.

This probably won't work so great with floating point values (due to precision), unless you floor/ceil the selection, but then you might run out of integers, so you may need to scale a bit... something like group e by Math.Floor((x - (x % f)) * scaleFactor).

Answer 2

This should do what you want

static int GetBucket(double value, double min, double max, int bucketCount)
{
    return (int)((value - min) / (max - min) * bucketCount + 0.5);
}

var grouped = input.GroupBy(e => GetBucket(e.Depth, 1, 100, 50));