Two arrays into a 2D Histogram

I’m using OxyPlot with F#. I have code to create a single parameter histogram and plot it. My code for dual parameter histograms in the form of a contour is too time consuming. I’d like an efficient way to map two vectors or arrays into a 2D histogram. I’m including my code for regular histogram.

    let myHistogram c =
    flatten dataArray.[c..c,*] 
    |> Seq.toArray
    |> (fun x -> round(float(x)/16.0))
    |> Seq.countBy (fun x -> x)
    |> Seq.sort
    |> snd

So, I’m looking to take dataArray.[a…a,*], dataArray[b…b,*] and place them into bins of a specific resolution to create histogram[x,y]. OxyPlot needs the histogram in order to create a contour.