dm1sh/polynomial_interpolation
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Commented coefficients functions

Browse Source
This commit is contained in:
Dmitriy Shishkov 2021-10-31 16:52:34 +03:00
parent c8682c7563
commit c0c5e219ea
No known key found for this signature in database
GPG Key ID: 14358F96FCDD8060
1 changed files with 18 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
main.c
View File

@ -38,26 +38,31 @@ double *div_diff_es(double *x, double *y, unsigned int n)
Coeficients of simplified polynomial computation Coeficients of simplified polynomial computation
*/ */
/* Simplifies Newton polynomial with `el_coef` array of divided differences,
and `x` as array of x coordinates of dots,
and `n` is number of elements of this sum */
void simplify_polynomial(double *res, double *el_coef, double *x, unsigned int n) void simplify_polynomial(double *res, double *el_coef, double *x, unsigned int n)
{ {
double *tmp_polynomial = (double *)malloc(sizeof(double) * n); double *tmp_polynomial // Temporary array for storage of coefficients of multiplication of (x-x_i) polynomial
tmp_polynomial[0] = 1; = (double *)malloc(sizeof(double) * n);
tmp_polynomial[0] = 1; // Set polynomial to 1 to start multiplication with it
for (int i = 0; i < n; i++) for (int i = 0; i < n; i++) // For each elemnt of sum
if (el_coef[i])
{ {
if (i > 0) if (i > 0) // Start multiplication from second element of sum
mult_by_root(tmp_polynomial, x[i - 1], i - 1); mult_by_root(tmp_polynomial, x[i - 1], i - 1);
for (int j = 0; j <= i; j++) for (int j = 0; j <= i; j++) // For each cumputed coefficient of i'th polynomial of sum
res[j] += el_coef[i] * tmp_polynomial[j]; res[j] += el_coef[i] * tmp_polynomial[j]; // Add it, multiplied with divided difference, to sum
} }
} }
void mult_by_root(double *res, double root, unsigned int step) /* `res` is an array of coefficients of polynomial which is multiplied with (x - `root`) polynomial
`power` is the power of `res` polynomial */
void mult_by_root(double *res, double root, unsigned int power)
{ {
for (int j = step + 1; j >= 0; j--) for (int j = power + 1; j >= 0; j--)
res[j] = (j ? res[j - 1] : 0) - (root * res[j]); res[j] = (j ? res[j - 1] : 0) - (root * res[j]); // coefficient is k_i-1 - root * k_i
} }
/* /*