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// 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;
PLINT nlegend;
PLCHAR_VECTOR text[2], symbols[2];
PLINT opt_array[2];
PLINT text_colors[2];
PLINT line_colors[2];
PLINT line_styles[2];
PLFLT line_widths[2];
PLINT symbol_numbers[2], symbol_colors[2];
PLFLT symbol_scales[2];
PLFLT legend_width, legend_height;
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 / M_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( 2 );
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)" );
nlegend = 1;
// 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 );
plstring( 101, freql, phase, "#(728)" );
plcol0( 3 );
plmtex( "r", 5.0, 0.5, 0.5, "Phase shift (degrees)" );
nlegend = 2;
}
// Draw a legend
// First legend entry.
opt_array[0] = PL_LEGEND_LINE;
text_colors[0] = 2;
text[0] = "Amplitude";
line_colors[0] = 2;
line_styles[0] = 1;
line_widths[0] = 1.;
// note from the above opt_array the first symbol (and box) indices
// do not have to be specified, at least in C. For Fortran we need
// to set the symbols to be something, since the string is always
// copied as part of the bindings.
symbols[0] = "";
// Second legend entry.
opt_array[1] = PL_LEGEND_LINE | PL_LEGEND_SYMBOL;
text_colors[1] = 3;
text[1] = "Phase shift";
line_colors[1] = 3;
line_styles[1] = 1;
line_widths[1] = 1.;
symbol_colors[1] = 3;
symbol_scales[1] = 1.;
symbol_numbers[1] = 4;
symbols[1] = "#(728)";
// from the above opt_arrays we can completely ignore everything
// to do with boxes.
plscol0a( 15, 32, 32, 32, 0.70 );
pllegend( &legend_width, &legend_height,
PL_LEGEND_BACKGROUND | PL_LEGEND_BOUNDING_BOX, 0,
0.0, 0.0, 0.1, 15,
1, 1, 0, 0,
nlegend, opt_array,
1.0, 1.0, 2.0,
1., text_colors, (const char **) text,
NULL, NULL, NULL, NULL,
line_colors, line_styles, line_widths,
symbol_colors, symbol_scales, symbol_numbers, (const char **) symbols );
}
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