File:Swastika curve.svg

#include    <stdio.h>
#include    <stdlib.h>
#include    <math.h>
#include    <unistd.h>
#include    <plplot/plplot.h>

long unsigned int NUM_PTS = 10000;
PLINT XMAX = 2;
PLINT YMAX = 2;

void generateCurve(PLFLT *x, PLFLT *y)
{
    int i = 0;
    double r, theta=0.f;
    float step = 2*PI/NUM_PTS;
    float s, c;
   
    while(theta < 2*PI)
    {
        s = sin(theta);        c = cos(theta);
        r = sqrt(s * c / (pow(s,4) - pow(c,4)));
        x[i] = (PLFLT) (r * cos(theta));
        y[i] = (PLFLT) (r * sin(theta));
        /*
        x[i] = (PLFLT) cos(theta) * sqrt(-1/sin(theta*4)) * modulus(sin(2*theta));
        y[i] = (PLFLT) sin(theta) * sqrt(-1/sin(theta*4)) * modulus(sin(2*theta));
        */
        theta += (double) step;
        i++;
    }
}

int main(void)
{
    PLFLT *X = NULL, *Y = NULL;
    plscolbg(255, 255, 255);
    plsdev("wxwidget");
    plinit();   // initialize plotting library
    plscol0(15, 0, 0, 0);
    plcol(15);
    plenv(-XMAX, XMAX, -YMAX, YMAX, 1, -2);
    plbox( "abcstn", 0, 0, "anbcst", 0, 0);
    pllab("X", "Y", "Swastika Curve");
    X = (PLFLT*) malloc(NUM_PTS * sizeof(PLFLT*));
    Y = (PLFLT*) malloc(NUM_PTS * sizeof(PLFLT*));
    if(X == NULL &#x7C;&#x7C; Y == NULL) 
    {
        perror("Unable to allocate memory!!");
        free(X);   free(Y);     exit(1);
    }
    generateCurve(X, Y);
    plline(NUM_PTS, X, Y);
    plend();    // close the plotting library
    { free(X);   free(Y); }
    return 0;
}