tomwalters@0: /*
tomwalters@0:     chi.c       repetitative chi-squared curve.
tomwalters@0: 
tomwalters@0: Examples:
tomwalters@0: 
tomwalters@0: chi amp=500 asym=1 per=4ms | x11plot
tomwalters@0: chi amp=500 asym=1 per=16ms | x11plot -n512
tomwalters@0: chi amp=500 asym=4 per=16ms | x11plot -n512
tomwalters@0: 
tomwalters@0: */
tomwalters@0: 
tomwalters@0: #include <stdio.h>
tomwalters@0: #include <math.h>
tomwalters@0: #include "options.h"
tomwalters@0: #include "units.h"
tomwalters@0: #include "strmatch.h"
tomwalters@0: 
tomwalters@0: char applic[]  = "generate a repeated chi-squared waveform. " ;
tomwalters@0: char usage[]   = "chi [options]" ;
tomwalters@0: 
tomwalters@0: static char *helpstr, *debugstr, *sampstr, *perstr, *astr, *asymstr, *dstr, *datastr ;
tomwalters@0: 
tomwalters@0: static Options option[] = {
tomwalters@0:     {   "help"      ,   "off"       ,  &helpstr     ,   "help"                     , DEBUG   },
tomwalters@0:     {   "debug"     ,   "off"       ,  &debugstr    ,   "debugging switch"         , DEBUG   },
tomwalters@0:     {   "samplerate",   "20kHz"     ,  &sampstr     ,   "samplerate "              , VAL     },
tomwalters@0:     {   "period"    ,   "8ms"       ,  &perstr      ,   "period [s,ms,p] of repetition"  , VAL     },
tomwalters@0:     {   "amplitude" ,   "1024"      ,  &astr        ,   "amplitude of waveform"    , VAL     },
tomwalters@0:     {   "asymmetry" ,   "1.0"       ,  &asymstr     ,   "parameter controlling assymmetry (>=1)"      , VAL     },
tomwalters@0:     {   "duration"  ,   "500ms"     ,  &dstr        ,   "duration of waveform"     , VAL     },
tomwalters@0:     {   "datatype"  ,   "short"     ,  &datastr     ,   "o/p datatype (short/float)", VAL     },
tomwalters@0:    ( char * ) 0 } ;
tomwalters@0: 
tomwalters@0: 
tomwalters@0: #define e   ( 2.718 )
tomwalters@0: 
tomwalters@0: int     samplerate ;
tomwalters@0: int     amplitude  ;
tomwalters@0: int     duration   ;
tomwalters@0: int     period     ;
tomwalters@0: float   a          ;
tomwalters@0: 
tomwalters@0: main(argc, argv)
tomwalters@0: int   argc ;
tomwalters@0: char *argv[] ;
tomwalters@0: {
tomwalters@0:     int    i, n, t ;
tomwalters@0:     short  s ;
tomwalters@0:     float  f ;
tomwalters@0:     float  b ;
tomwalters@0:     float  r = 4 ;
tomwalters@0: 
tomwalters@0:     getopts( option,argc,argv ) ;
tomwalters@0:     if ( !isoff( helpstr ) )
tomwalters@0: 	helpopts3( helpstr, argv[0], applic, usage, option ) ;
tomwalters@0: 
tomwalters@0:     samplerate = to_Hz( sampstr, 0 ) ;
tomwalters@0:     amplitude  = atoi( astr ) ;
tomwalters@0:     period     = (int)to_p( perstr, samplerate ) ;
tomwalters@0:     a          = atof( asymstr ) ;
tomwalters@0:     duration   = to_p( dstr, samplerate )   ;
tomwalters@0: 
tomwalters@0:     b = ( 2. * a ) / period ;   /* sets mode at half-way to period */
tomwalters@0: 
tomwalters@0:     if ( iststr( datastr, "short" ) )
tomwalters@0: 	for ( i=0 ; i<duration ;  )
tomwalters@0: 	    for ( t=0 ; t<period*r && i<duration ; t+=r, i++ ) {
tomwalters@0: 		s = amplitude * pow( (double)( ( e * b * t ) / a ), (double)a ) * exp( -(double)( b * t ) ) ;
tomwalters@0: 		fwrite( &s, sizeof(short), 1, stdout ) ;
tomwalters@0: 	    }
tomwalters@0:     else if ( iststr( datastr, "float" ) )
tomwalters@0: 	for ( i=0 ; i<duration ;  )
tomwalters@0: 	    for ( t=0 ; t<period && i<duration ; t++, i++ ) {
tomwalters@0: 		f = amplitude * pow( (double)( ( e * b * t ) / a ), (double)a ) * exp( -(double)( b * t ) ) ;
tomwalters@0: 		fwrite( &f, sizeof(float), 1, stdout ) ;
tomwalters@0: 	    }
tomwalters@0:     else
tomwalters@0: 	fprintf(stderr,"unknown datatype [%s]\n", datastr) ;
tomwalters@0: }