module Bode (bodeplot) where


-- TODO: make proper bode plots.
import Graphics.Gnuplot.Simple
import Data.Complex

-- Uses Gnuplot "set" command to set any options not directly
-- supported by the wrapper.  See also 
-- http://en.wikipedia.org/wiki/File:Bode_plot_template.pdf
logAttrib = [
 XLabel "Freqency (Hz)",
-- LineStyle 1 [LineTitle "foobar"],
 Custom "xrange" ["[20:20000]"],
 Custom "grid" [],
 Custom "logscale" ["x", "10"], 
 Custom "logscale" ["y", "10"]]

-- Standard scale for audio plots. 4 decades at 5Hz -> 50kHz.
logScale low high n = map e [0..n] where
    e i = low * (high / low) ** (i / n)

bodeplot fn = plotFunc logAttrib audioScale (amplitude fn) where
    amplitude fn = \f -> magnitude $ fn (0 :+ 2 * pi * f)
    audioScale = logScale 20 20000 1000