42 lines
811 B
C
42 lines
811 B
C
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/* Driver for routine spline */
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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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#include "nrutil.h"
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#define N 20
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#define PI 3.1415926
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int main(void)
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{
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int i;
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float yp1,ypn,*x,*y,*y2;
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x=vector(1,N);
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y=vector(1,N);
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y2=vector(1,N);
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printf("\nsecond-derivatives for sin(x) from 0 to pi\n");
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/* Generate array for interpolation */
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for (i=1;i<=20;i++) {
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x[i]=i*PI/N;
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y[i]=sin(x[i]);
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}
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/* calculate 2nd derivative with spline */
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yp1=cos(x[1]);
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ypn=cos(x[N]);
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spline(x,y,N,yp1,ypn,y2);
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/* test result */
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printf("%23s %16s\n","spline","actual");
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printf("%11s %14s %16s\n","angle","2nd deriv","2nd deriv");
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for (i=1;i<=N;i++)
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printf("%10.2f %16.6f %16.6f\n",x[i],y2[i],-sin(x[i]));
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free_vector(y2,1,N);
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free_vector(y,1,N);
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free_vector(x,1,N);
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return 0;
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}
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#undef NRANSI
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