Creating Spectral Heat maps or Intensity maps from CDIP data using Ruby

Question

BACKGROUND

Per the Coastal Information Data Program (CDIP), they are generating a spectral heat/intensity map for wave swell at http://cdip.ucsd.edu

Answer 1

Chip, I know, not using Ruby, but assuming that Belisarius's point calculation is fine, I'd use Mathematica's ListContourPlot instead, as it is much simpler to understand and it gives a cleaner picture.

(* Read in data, the web address can be specified *)
a = Import[, "Table"];

Import leaves in a pre tag in the first sublist and as a single element sublist at the end, this removes it

dat = a[[ ;; -2]][[All, -72;; ]];

by first taking all but the last element, and then taking the last 72 elements of each remaining sublists.

ListContourPlot expects a list of points of the form {{x, y, f}, ...}, so we need to transform dat into that form, as explained elsewhere:

pts =Flatten[
    Table[ {
          (rr =Log[.025 + (.58 - .25)/64 r]) Cos@(tt = t 5 Degree), (* x-coord *)
          rr Sin@tt, (* y-coord *)
          dat[[r,t]] (* function value *)
           },
           {r, 7, 64}, {t, 1, 72}
         ],
    1 ]

and then plot them

ListContourPlot[pts,
  ColorFunctionScaling -> False,
  ColorFunction -> (ColorData["CMYKColors"][(# - .000007)/(.0003 - 0.000007)]&)
  ]

This gives:

which can be touched up by fixing the clipping and the ColorFunction scaling. Also, with some work radial contours could be added.