Simpler way to calculate angle between two points?

[appel]

I'd like to know if there is a simpler way to calculate the angle between two points.

I'm currently using this method:

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public static float angle(float x1, float y1, float x2, float y2)     {         float dx=x2-x1,dy=y2-y1, PI=(float)Math.PI;         double angle=0.0f;                 if(dx==0)            if(dy==0)angle=0;            else if(dy>0)angle=PI/2;            else angle=PI*3/2;         else if(dy==0)            if(dx>0)angle=0;            else angle=PI;         else if(dx<0)angle=Math.atan(dy/dx)+PI;         else if(dy<0)angle=Math.atan(dy/dx)+(2*PI);         else angle=Math.atan(dy/dx);         return (float)angle;     }

Seems like a awful alot for something simple as that.

I'd like the angle to be 0 at 3 o'clock, and moving clockwise it should be PI at 9 o'clock. Any ideas?

[kul_th_las]

I would write it slightly different, but I think what you've got there is as simple as it gets when you're starting with a pair of (x, y) coordinates.

You could change your logic around a bit so you don't have so many if/then/else statements, but it doesn't look like you're doing any wasted work.

[kevglass]

Math.atan2() does this doesn't it?

Kev

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[woogley]

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protected double calcAngle(Point p1,Point p2) {      return Math.atan2(p2.y-p1.y,p2.x-p1.x)*180.0/Math.PI; }

[appel]

Amazing, thanks kev and woogley. That was exactly the *simplicity* I was looking for