arrays - 2D interpolation in C -


so program supposed ask user temperature in kelvins , starting ne. , interpolate find given value.

the temp array temperatures , used find temperature between.

the n array ne's , used find ne between.

whatever spots in each end being spot interpolating in bigger array, hpe.

the main function ask user temperature , ne , calls upon interpolation function.

the interpol function function interpolates. first finds given temperature in temp array. finds given ne in n array. uses spot (hpe[k][l]) 2d interpolation.

my problem when run , enter values should giving me answer, "the value determined nan"

what doing wrong?

#include <stdio.h> #include <stdlib.h> #include <math.h>  double interpol(double ti, double ne);  int main() {     int ni;     double ti, result, ne;      printf("\nenter temperature in kelvins , ne separated space.\n");     ni = scanf("%lf %lf", &ti, &ne);     result = interpol(ti, ne);     printf("\nthe value determined %lf\n", result); }   double interpol(double ti, double ne) {     int i, j, k, l;     double y1, y2, y3, y4, t, u, p;     double temp[15] = {         1000.0, 2000.0, 3000.0, 4000.0, 5000.0,         6000.0, 7000.0, 8000.0, 9000.0, 10000.0,         11000.0, 12000.0, 13000.0, 14000.0, 15000.0};     double n[8] = {10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0};     double hpe[15][8] = {         {0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0},         {0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0},         {0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0},         {0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0},         {0.0017, 0.0002, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0},         {0.2980, 0.0407, 0.0042, 0.0004, 0.0, 0.0, 0.0, 0.0},         {0.9582, 0.6961, 0.1864, 0.0224, 0.0023, 0.0002, 0.0, 0.0},         {0.9979, 0.9791, 0.8241, 0.3191, 0.0448, 0.0047, 0.0005, 0.0},         {0.9998, 0.9980, 0.9804, 0.8335, 0.3335, 0.0477, 0.0050, 0.0005},         {1.0, 0.9997, 0.9971, 0.9713, 0.7719, 0.2529, 0.0327, 0.0034},         {1.0, 0.9999, 0.9994, 0.9939, 0.9425, 0.6211, 0.1408, 0.0161},         {1.0, 1.0, 0.9998, 0.9984, 0.9841, 0.8606, 0.3817, 0.0581},         {1.0, 1.0, 0.9999, 0.9995, 0.9948, 0.9503, 0.6568, 0.1607},         {1.0, 1.0, 1.0, 0.9998, 0.9980, 0.9807, 0.8358, 0.3373},         {1.0, 1.0, 1.0, 0.9999, 0.9992, 0.9917, 0.9229, 0.5448}     };      (i = 1 ; < 16 ; i++)     {         if (temp[i] <= ti && temp[i+1] >= ti)         {             k = i;             break;         }     }      (j = 1 ; j < 9 ; j++)     {         if (n[j] <= ne && n[j+1] >= ne)         {             l = j;             break;         }     }      y1 = hpe[k][l];     y2 = hpe[k+1][l];     y3 = hpe[k+1][l+1];     y4 = hpe[k][l+1];      t = (ti - (hpe[k][0])) / ((hpe[k+1][0]) - (hpe[k][0]));     u = (ne - (hpe[0][l])) / ((hpe[0][l+1]) - (hpe[0][l]));     p = ((1 - t) * (1 - u) * y1) + (t * (1 - u) * y2) + (t * u * y3) + ((1 - t) * u * y4);      return (p); }

you have obvious mistake programmer, arrays of size n in indexed 0 n - 1. there languages array of size n indexed 1 n example, in it's 0 n - 1.


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