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/* $Id: x04c.c,v 1.17 2002/12/03 08:39:24 airwin Exp $
Log plot demo.
*/
#include "plcdemos.h"
void plot1(int type);
/*--------------------------------------------------------------------------*\
* main
*
* Illustration of logarithmic axes, and redefinition of window.
\*--------------------------------------------------------------------------*/
int
main(int argc, char *argv[])
{
/* Parse and process command line arguments */
(void) plParseOpts(&argc, argv, PL_PARSE_FULL);
/* Initialize plplot */
plinit();
plfont(2);
/* Make log plots using two different styles. */
plot1(0);
plot1(1);
plend();
exit(0);
}
/*--------------------------------------------------------------------------*\
* plot1
*
* Log-linear plot.
\*--------------------------------------------------------------------------*/
void
plot1(int type)
{
int i;
static PLFLT freql[101], ampl[101], phase[101];
PLFLT f0, freq;
pladv(0);
/* Set up data for log plot */
f0 = 1.0;
for (i = 0; i <= 100; i++) {
freql[i] = -2.0 + i / 20.0;
freq = pow(10.0, freql[i]);
ampl[i] = 20.0 * log10(1.0 / sqrt(1.0 + pow((freq / f0), 2.)));
phase[i] = -(180.0 / PI) * atan(freq / f0);
}
plvpor(0.15, 0.85, 0.1, 0.9);
plwind(-2.0, 3.0, -80.0, 0.0);
/* Try different axis and labelling styles. */
plcol0(1);
switch (type) {
case 0:
plbox("bclnst", 0.0, 0, "bnstv", 0.0, 0);
break;
case 1:
plbox("bcfghlnst", 0.0, 0, "bcghnstv", 0.0, 0);
break;
}
/* Plot ampl vs freq */
plcol0(2);
plline(101, freql, ampl);
plcol0(1);
plptex(1.6, -30.0, 1.0, -20.0, 0.5, "-20 dB/decade");
/* Put labels on */
plcol0(1);
plmtex("b", 3.2, 0.5, 0.5, "Frequency");
plmtex("t", 2.0, 0.5, 0.5, "Single Pole Low-Pass Filter");
plcol0(2);
plmtex("l", 5.0, 0.5, 0.5, "Amplitude (dB)");
/* For the gridless case, put phase vs freq on same plot */
if (type == 0) {
plcol0(1);
plwind(-2.0, 3.0, -100.0, 0.0);
plbox("", 0.0, 0, "cmstv", 30.0, 3);
plcol0(3);
plline(101, freql, phase);
plcol0(3);
plmtex("r", 5.0, 0.5, 0.5, "Phase shift (degrees)");
}
}
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