51 lines
956 B
C
51 lines
956 B
C
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/* Driver for routine chebft */
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#include <stdio.h>
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#include <math.h>
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#define NRANSI
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#include "nr.h"
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#define NVAL 40
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#define PIO2 1.5707963
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float func(float x)
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{
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return x*x*(x*x-2.0)*sin(x);
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}
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int main(void)
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{
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float a=(-PIO2),b=PIO2,dum,f;
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float t0,t1,term,x,y,c[NVAL];
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int i,j,mval;
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chebft(a,b,c,NVAL,func);
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/* test result */
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for (;;) {
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printf("\nHow many terms in Chebyshev evaluation?\n");
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printf("Enter n between 6 and %2d. (n=0 to end).\n",NVAL);
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scanf("%d",&mval);
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if ((mval <= 0) || (mval > NVAL)) break;
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printf("\n%9s %14s %16s\n","x","actual","chebyshev fit");
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for (i = -8;i<=8;i++) {
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x=i*PIO2/10.0;
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y=(x-0.5*(b+a))/(0.5*(b-a));
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/* Evaluate Chebyshev polynomial without CHEBEV */
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t0=1.0;
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t1=y;
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f=c[1]*t1+c[0]*0.5;
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for (j=2;j<mval;j++) {
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dum=t1;
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t1=2.0*y*t1-t0;
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t0=dum;
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term=c[j]*t1;
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f += term;
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}
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printf("%12.6f %12.6f %12.6f\n",x,func(x),f);
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}
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}
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return 0;
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}
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#undef NRANSI
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