plsmooth

performs a k-point smoothing on an array

parameter	type	units	description
array	float*	uu	array to be smoothed
n	int	--	length of array
k	int	--	number of points of the smooth (must be odd)
returns:	void

Description

plsmooth applies a k-point (k must be odd and < n) quartic-cubic smooth to the n values in array. The first and last k/2 points in a are unaffected.

see c.g.enke, t.a.nieman, anal. chem. vol 48, page 705a

Examples

/* __________ plsmooth __________
  plotting a noise modulated sine with and without smoothing
  features: use of plaxfit, plpline, plformat
            smoothing
*/
#include <stdlib.h>
#include <math.h>
#include <simplot.h>
#define NPOINTS 200
#define RANGE 23
int main() {
   float x[NPOINTS],y[NPOINTS];
   int i;
   plinit(PS,"plsmooth",A4,50,50,"","");

   for (i=0;i<NPOINTS;i++)     // loop generates the noise-modulated sine data
   { x[i]=i/10.;
      y[i]=sin(x[i])+(float)rand()/RAND_MAX-.5;
   }
   plaxfit(x,y,NPOINTS,10,130,80,"@a@ (radians)","sin @a@"," ");
   // fits axes to the data
   plotm(0,0,UP);
   plformat(.5,-.5,"\n%d-point smooth of noisy sine",RANGE);
   // report smoothing range
   plset(HEIGHT,1);                // make symbols small giving dots
   plpline(x,y,NPOINTS,"O",UP);    /* plot unsmoothed data.
                                        mark with O's, no connecting line */
   if (plget(PLOTTER)!=PS)
      plcolor(Red);
   plsmooth(y,NPOINTS,RANGE);      // smooth the data
   plpline(x,y,NPOINTS,"",DOWN);   // and plot again. no marking symbols
   plframe(5,3);
   plend();
   exit(0);
}

plsmooth