mirror of https://github.com/Askill/AP-SCE.git
107 lines
3.2 KiB
C++
107 lines
3.2 KiB
C++
#include "mex.h"
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#include "matrix.h"
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#include "stdlib.h"
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#include "math.h"
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void mexFunction(int nlhs, mxArray *plhs[], // Output variables
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int nrhs, const mxArray *prhs[]) // Input variables
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{
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if (nrhs != 4)
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mexErrMsgTxt ("Check your input parameters");
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if( mxGetNumberOfElements(prhs[2]) != mxGetNumberOfElements(prhs[3]))
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{
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mexErrMsgTxt ("arrays need to be of same size!");
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}
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int variables = *mxGetPr(prhs[0]);
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double inc = *mxGetPr(prhs[1]);
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double* x = (double *)mxCalloc(variables, sizeof(double)); //create solution array
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double* x_in = (double *)mxCalloc(variables, sizeof(double)); //input x
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double* y = (double *)mxCalloc(variables, sizeof(double)); //input y
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double** GA = (double **)mxCalloc(variables+1, sizeof(double*)); //create Gauss Array (GA)
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for (int i = 0; i <= variables; i++){
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GA[i] = (double *)mxCalloc(variables+1, sizeof(double));
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}
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for(int i=0;i<variables;i++){
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x_in[i]=mxGetPr(prhs[2])[i];
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}
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for(int i=0;i<variables;i++){
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y[i]=mxGetPr(prhs[3])[i];
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}
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for(int i=0;i<variables;i++){ //fill GA with the polynoms
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for(int j=0; j<variables;j++){
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GA[i][j] = pow(x_in[i],j);
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}
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}
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for(int i=0;i<variables;i++){
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GA[i][variables] = y[i];
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}
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double len = (x_in[variables-1]-x_in[0])/inc +1;
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double* xx = (double *)mxCalloc(len, sizeof(double)); //return array with x values
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double* yy = (double *)mxCalloc(len, sizeof(double)); //return array with interpolated y values
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double temp=x_in[0];
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for(int i=0;temp <= x_in[variables-1]+inc;i++){ //generate return array with x values
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xx[i]=temp;
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temp += inc;
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}
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// Gauß
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for (int i = 0; i<variables; i++) //Pivotisation
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for (int k = i + 1; k<variables; k++)
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if (abs(GA[i][i])<abs(GA[k][i]))
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for (int j = 0; j <= variables; j++)
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{
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long double temp = GA[i][j];
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GA[i][j] = GA[k][j];
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GA[k][j] = temp;
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}
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for (int i = 0; i<variables - 1; i++) //gauss elimination
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for (int k = i + 1; k<variables; k++)
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{
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long double t = GA[k][i] / GA[i][i];
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for (int j = 0; j <= variables; j++)
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GA[k][j] = GA[k][j] - t*GA[i][j]; //make the elements below the pivot elements equal to zero or elimnate the variables
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}
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for (int i = variables - 1; i >= 0; i--) //back-substitution
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{ //x is an array whose values correspond to the values of x,y,z..
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x[i] = GA[i][variables]; //make the variable to be calculated equal to the rhs of the last equation
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for (int j = i + 1; j<variables; j++)
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if (j != i) //then subtract all the lhs values except the coefficient of the variable whose value is being calculated
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x[i] = x[i] - GA[i][j] * x[j];
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x[i] = x[i] / GA[i][i]; //now finally divide the rhs by the coefficient of the variable to be calculated
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}
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//polyval: filling yy with the interpolated values
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for (int i = 0; i < len; i++){
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double tmp = 0;
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for (int j = 0; j < variables; j++){
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tmp += pow(xx[i], j) * x[j];
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}
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yy[i]=tmp;
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}
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//return values
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nlhs = 2;
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plhs[0] = mxCreateDoubleMatrix(1, len, mxREAL);
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memcpy(mxGetPr(plhs[0]), xx, len*sizeof(double));
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plhs[1] = mxCreateDoubleMatrix(1, len, mxREAL);
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memcpy(mxGetPr(plhs[1]), yy, len*sizeof(double));
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//free memory
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// causes errors
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return;
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} |