please help me to correct axis direction

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My aim to get direction based on two cordinates x1 and x2

here

center=x1;
pointOncircle=x2;

C#

if (center.X < pointOnCircle.X)
             {
                 UpdateText("right");

             }
             else if (center.X >pointOnCircle.X)
             {

                 UpdateText("left");

             }
             else if (center.Y < pointOnCircle.Y)
             {
                 UpdateText("down");

             }
             else {

                 UpdateText("up");


             }

Posted 23-Jun-13 3:33am

vishnulalr

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OriginalGriff · Answer 1 · 2013-06-23T03:57:00

Solution 1

Don't do that: work out the angle of a line between the two points instead.

C#

double angle(Point p1, Point p2)
    {
    double xDiff = p2.X - p1.X;
    double yDiff = p2.Y - p1.Y;
    return Math.Atan2(yDiff, xDiff) * (180 / Math.PI);
    }

Then all you have to do is look at the value:
between 45 and -45 is Right, and so forth.

Posted 23-Jun-13 3:57am

OriginalGriff

Comments

vishnulalr 23-Jun-13 10:05am

thanks for you reply it help me a lot but how can i get for up down ? i have got another snipet is that good for me it almost works

float xCentroidsDifference = center.X - pointOnCircle.X;
float yCentroidsDifference = center.Y - pointOnCircle.Y;

float threshold = 50;

UpdateText5("center");
if (Math.Abs(xCentroidsDifference) > Math.Abs(yCentroidsDifference))
{
if (xCentroidsDifference > threshold)
UpdateText5( "right");
if (xCentroidsDifference < -threshold)
UpdateText5("left");
}
if (Math.Abs(xCentroidsDifference) < Math.Abs(yCentroidsDifference))
{
if (yCentroidsDifference > threshold)
UpdateText5("up");
if (yCentroidsDifference < -threshold)
UpdateText5("down");
}

OriginalGriff 23-Jun-13 10:13am

How do you think it works for up and down?
If Right is 45 to -45, then up is 46 to 45 + 90, and so forth...
Try looking at the numbers you get for (0, 0) and (0, 100) for example - that's directly up on most graphs...