cartesian_to_polar.c File Reference

Function to convert a Cartesian co-ordinate to polar form. More...

#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

Include dependency graph for cartesian_to_polar.c:

Macros
#define	_USE_MATH_DEFINES
	required for MS Visual C

Functions
void	to_polar (double x, double y, double *r, double *theta)
	Function to convert cartesian coordinates to polar. More...
double	get_rand (double lim1, double lim2)
	Generate a random number in the given limits. More...
void	test ()
	Test implementation.
int	main ()
	Main function.

Detailed Description

Function to convert a Cartesian co-ordinate to polar form.

Function Documentation

get_rand()

double get_rand	(	double	lim1,
		double	lim2
	)

Generate a random number in the given limits.

Parameters

lim1	lower limit
lim2	upper limit

Returns

random number in the given range

{
    double r = (double)rand() / RAND_MAX;  // value in [0,1)
    return (lim2 - lim1) * r + lim1;       // scale to range
}

to_polar()

void to_polar	(	double	x,
		double	y,
		double *	r,
		double *	theta
	)

Function to convert cartesian coordinates to polar.

\begin{eqnarray*} r &=& \sqrt{x^2+y^2}\\ \theta &=& \atan\frac{y}{x} \end{eqnarray*}

Parameters

[in]	x	absicca value
[in]	y	ordinate value
[out]	r	pointer to store polar radius
[out]	theta	pointer to store polar angle (in radian)

{
    double thetaFinal = 0.f;
 
    *r = sqrt(x * x + y * y);
 
    if (x != 0)
    {
        if (y != 0)
        {
            *theta = atan(y / x);
            if ((x > 0 && y > 0) || (x == -y))
            {  // Q1
                thetaFinal = *theta;
            }
            else if (x < 0 && y > 0)
            {  // Q2
                thetaFinal = *theta + M_PI;
            }
            else if (x < 0 && y < 0)
            {  // Q3
                thetaFinal = *theta - M_PI;
            }
            else if (x > 0 && y < 0)
            {  // Q4
                thetaFinal = 2 * M_PI - *theta;
            }
            else
            {
                fprintf(stderr, "Should not reach here!\n");
            }
        }
    }
    else
    {  // exceptions when no actual angle is present
        if (y > 0)
        {
            thetaFinal = M_PI / 2;
        }
        else
        {
            thetaFinal = -(M_PI / 2);
        }
    }
    if (y == 0)
    {
        if (x > 0)
        {
            thetaFinal = 0;
        }
        else
        {
            thetaFinal = -M_PI;
        }
    }
 
    *theta = thetaFinal;
}