--[[ $Id: x04.lua 12331 2013-05-03 02:41:21Z airwin $

	Log plot demo.
	Simple line plot and multiple windows demo.

  Copyright (C) 2008  Werner Smekal

  This file is part of PLplot.

  PLplot is free software you can redistribute it and/or modify
  it under the terms of the GNU Library General Public License as published
  by the Free Software Foundation either version 2 of the License, or
  (at your option) any later version.

  PLplot is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU Library General Public License for more details.

  You should have received a copy of the GNU Library General Public License
  along with PLplot if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
--]]

-- initialise Lua bindings for PLplot examples.
dofile("plplot_examples.lua")

----------------------------------------------------------------------------
-- plot1
--
-- Log-linear plot.
----------------------------------------------------------------------------

-- return single bit (for OR)
function bit(x,b)
  return ((x % 2^b) - (x % 2^(b-1)) > 0)
end

-- logic OR for number values

function lor(x,y)
  result = 0
  for p=1,8 do result = result + (((bit(x,p) or bit(y,p)) == true) and 2^(p-1) or 0) end
  return result
end

function plot1(type)
  freql = {}
  ampl = {}
  phase = {}

  pl.adv(0)

  -- Set up data for log plot 
  f0 = 1
  for i=1, 101 do
    freql[i] = -2 + (i-1) / 20
    freq = 10^freql[i]
    ampl[i] = 20 * math.log10(1 / math.sqrt(1 + (freq / f0)^2))
    phase[i] = -(180 / math.pi) * math.atan(freq / f0)
  end

  pl.vpor(0.15, 0.85, 0.1, 0.9)
  pl.wind(-2, 3, -80, 0)

  -- Try different axis and labelling styles. 
  pl.col0(1)
  if type == 0 then
    pl.box("bclnst", 0, 0, "bnstv", 0, 0)
  elseif type == 1 then
    pl.box("bcfghlnst", 0, 0, "bcghnstv", 0, 0)
  else
    print("error: type must be either 0 or 1")
  end
  
  -- Plot ampl vs freq 
  pl.col0(2)
  pl.line(freql, ampl)
  pl.col0(2)
  pl.ptex(1.6, -30, 1, -20, 0.5, "-20 dB/decade")

  -- Put labels on 
  pl.col0(1)
  pl.mtex("b", 3.2, 0.5, 0.5, "Frequency")
  pl.mtex("t", 2, 0.5, 0.5, "Single Pole Low-Pass Filter")
  pl.col0(2)
  pl.mtex("l", 5, 0.5, 0.5, "Amplitude (dB)")

  -- For the gridless case, put phase vs freq on same plot 
  if type == 0 then
    pl.col0(1)
    pl.wind(-2, 3, -100, 0)
    pl.box("", 0, 0, "cmstv", 30, 3)
    pl.col0(3)
    pl.line(freql, phase)
    pl.string(freql, phase, "*")
    pl.col0(3)
    pl.mtex("r", 5, 0.5, 0.5, "Phase shift (degrees)")
    nlegend = 2
  else
    nlegend = 1
  end

  -- Draw a legend.
  opt_array = {}
  text_colors = {}
  text = {}
  box_colors = {}
  box_patterns = {}
  box_scales = {}
  box_line_widths = {}
  line_colors = {}
  line_styles = {}
  line_widths = {}
  symbol_colors = {}
  symbol_scales = {}
  symbol_numbers = {}
  symbols = {}

  -- Data for the first legend entry.
  opt_array[1] = pl.PL_LEGEND_LINE
  text_colors[1] = 2
  text[1] = "Amplitude"
  -- box data unused so initialize to arbitrary values.
  box_colors[1] = 0
  box_patterns[1] = 0
  box_scales[1] = 0
  box_line_widths[1] = 0.
  line_colors[1] = 2
  line_styles[1] = 1
  line_widths[1] = 1.
  -- unused arbitrary data
  symbol_colors[1]  = 0
  symbol_scales[1]  = 0
  symbol_numbers[1] = 0
  symbols[1]        = ""

  -- Data for the second legend entry.
  if nlegend > 1 then
    opt_array[2]      = lor(pl.PL_LEGEND_LINE, pl.PL_LEGEND_SYMBOL)
    text_colors[2]    = 3
    text[2]           = "Phase shift"
  -- box data unused so initialize to arbitrary values.
    box_colors[2] = 0
    box_patterns[2] = 0
    box_scales[2] = 0
    box_line_widths[2] = 0.
    line_colors[2]    = 3
    line_styles[2]    = 1
    line_widths[2]    = 1.
    symbol_colors[2]  = 3
    symbol_scales[2]  = 1.
    symbol_numbers[2] = 4
    symbols[2]        = "*"
  end

  pl.scol0a( 15, 32, 32, 32, 0.70 )

  legend_width, legend_height = pl.legend(
    lor(pl.PL_LEGEND_BACKGROUND, pl.PL_LEGEND_BOUNDING_BOX), 0, 0.0, 0.0,
    0.1, 15, 1, 1, 0, 0, opt_array, 1.0, 1.0, 2.0,
    1., text_colors, text, 
    box_colors, box_patterns, box_scales, box_line_widths, 
    line_colors, line_styles, line_widths,
    symbol_colors, symbol_scales, symbol_numbers, symbols )
end

----------------------------------------------------------------------------
-- main
--
-- Illustration of logarithmic axes, and redefinition of window.
----------------------------------------------------------------------------

-- Parse and process command line arguments 
pl.parseopts(arg, pl.PL_PARSE_FULL)

-- Initialize plplot 
pl.init()
pl.font(2)

-- Make log plots using two different styles. 
plot1(0)
plot1(1)

pl.plend()
