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#!/usr/bin/env python
#
# x04c.c
#
# Log plot demo.
from numpy import *
import math
#import pl
import sys
import os
module_dir = "@MODULE_DIR@"
if module_dir[0] == '@':
module_dir = os.getcwd ()
sys.path.insert (0, module_dir)
# main
#
# Illustration of logarithmic axes, and redefinition of window.
def main(w):
## # Parse and process command line arguments
##
## pl.ParseOpts(sys.argv, pl.PARSE_FULL)
##
## # Initialize plplot
##
## pl.init()
w.pladv(0)
w.plfont(2)
f0 = 1000.0
freql = zeros(101,'d'); ampl = zeros(101,'d'); phase=zeros(101,'d')
## freql = []
## ampl = []
## phase = []
for i in range(101):
## freql.append(1.0 + i / 20.0)
freql[i] = 1.0 + i / 20.0
## freq = pow(10.0, freql[i])
freq = pow( 10.0, freql[i] )
## ampl.append(
## 20.0 * math.log10(1.0 / math.sqrt(1.0 + pow((freq / f0), 2.)))
## )
ampl[i] = 20.0 * math.log10(1.0 / math.sqrt(1.0 + pow((freq / f0), 2.)))
## phase.append(-(180.0 / math.pi) * math.atan(freq / f0))
phase[i] = -(180.0 / math.pi) * math.atan(freq / f0)
w.plvpor(0.15, 0.85, 0.1, 0.9)
w.plwind(1.0, 6.0, -80.0, 0.0)
w.plcol0(1)
w.plbox("bclnst", 0.0, 0, "bnstv", 0.0, 0)
w.plcol0(2)
w.plline(freql, ampl)
w.plcol0(1)
w.plptex(5.0, -30.0, 1.0, -20.0, 0.5, "-20 dB/decade")
w.plwind(1.0, 6.0, -100.0, 0.0)
w.plbox("", 0.0, 0, "cmstv", 30.0, 3)
w.plcol0(3)
w.plline(freql, phase)
w.plcol0(1)
w.plmtex("b", 3.2, 0.5, 0.5, "Frequency")
w.plmtex("t", 2.0, 0.5, 0.5, "Single Pole Low-Pass Filter")
w.plcol0(2)
w.plmtex("l", 5.0, 0.5, 0.5, "Amplitude (dB)")
w.plcol0(3)
w.plmtex("r", 5.0, 0.5, 0.5, "Phase shift (degrees)")
w.pleop()
##main()
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