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! $Id: x04f.f90,v 1.1 2006/05/16 20:24:12 airwin Exp $
! Illustration of logarithmic axes, and redefinition of window
!
! Copyright (C) 2004 Alan W. Irwin
!
! This file is part of PLplot.
!
! PLplot is free software; you can redistribute it and/or modify
! it under the terms of the GNU General Library 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
use plplot
implicit none
! Process command-line arguments
call plparseopts(PL_PARSE_FULL)
call plinit
call plfont(2)
! Make log plots using two different styles.
call plot1(0)
call plot1(1)
call plend
end
subroutine plot1(type)
use plplot, PI => PL_PI
implicit none
real(kind=plflt) freql(0:100),ampl(0:100),phase(0:100), freq, f0
integer i, type
call pladv(0)
! Set up data for log plot.
f0 = 1._plflt
do i=0,100
freql(i)= -2.0_plflt + dble (i)/20.0_plflt
freq=10.0_plflt**freql(i)
ampl(i)=20.0_plflt*log10(1.0_plflt/sqrt(1.0_plflt+(freq/f0)**2))
phase(i)=-(180.0_plflt/PI)*atan(freq/f0)
enddo
call plvpor(0.15_plflt, 0.85_plflt, 0.1_plflt, 0.9_plflt)
call plwind(-2.0_plflt, 3.0_plflt, -80.0_plflt, 0.0_plflt)
call plcol0(1)
! Try different axis and labelling styles.
if (type.eq.0) then
call plbox('bclnst', 0.0_plflt, 0, 'bnstv', 0.0_plflt, 0)
elseif (type.eq.1) then
call plbox('bcfghlnst', 0.0_plflt, 0, 'bcghnstv', 0.0_plflt, 0)
else
stop 'plot1: invalid type'
endif
! Plot ampl vs freq.
call plcol0(2)
call plline(freql,ampl)
call plcol0(1)
call plptex(1.6_plflt, -30.0_plflt, 1.0_plflt, -20.0_plflt, 0.5_plflt, &
'-20 dB/decade')
! Put labels on.
call plcol0(1)
call plmtex('b', 3.2_plflt, 0.5_plflt, 0.5_plflt, 'Frequency')
call plmtex('t', 2.0_plflt, 0.5_plflt, 0.5_plflt, &
'Single Pole Low-Pass Filter')
call plcol0(2)
call plmtex('l', 5.0_plflt, 0.5_plflt, 0.5_plflt, 'Amplitude (dB)')
! For the gridless case, put phase vs freq on same plot.
if(type.eq.0) then
call plcol0(1)
call plwind(-2.0_plflt, 3.0_plflt, -100.0_plflt, 0.0_plflt)
call plbox(' ', 0.0_plflt, 0, 'cmstv', 30.0_plflt, 3)
call plcol0(3)
call plline(freql,phase)
call plcol0(3)
call plmtex('r', 5.0_plflt, 0.5_plflt, 0.5_plflt, &
'Phase shift (degrees)')
endif
end
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