CODEWITHSUNDEEP
php
user1802209
user1802209

Reputation: 97

How to get the coordinates of several points on the circle with php

I have a few points. I need to put those points on a circle and get their coordinates.

function positionX($numItems,$thisNum){ 
  $alpha = 360/$numItems; // angle between the elements
  $r = 1000; // radius
  $angle = $alpha * $thisNum; // angle for N element
  $x = $r * cos($angle); // X coordinates
  return $x;
}

function positionY($numItems,$thisNum){ 
  $alpha = 360/$numItems; // angle between the elements
  $r = 1000; // radius
  $angle = $alpha * $thisNum; // angle for N element
  $y = $r * sin($angle); // Y coordinates
  return $y;
}

But my code isn't work.. These functions produce strange coordinates.

image example: http://cl.ly/image/453E2w1Y0w0d

UPD:

echo positionX(4,1)."<br>";
echo positionY(4,1)."<br><br>";

echo positionX(4,2)."<br>";
echo positionY(4,2)."<br><br>";

echo positionX(4,3)."<br>";
echo positionY(4,3)."<br><br>";

echo positionX(4,4)."<br>";
echo positionY(4,4)."<br><br>";

4 - All elements; 1,2,3,4 - Number of element.

These code gives me result:

-448.073616129
893.996663601

-598.460069058
0

984.381950633
-176.045946471

-283.691091487
958.915723414

On the circle it does not work.

Upvotes: 1

Views: 1461

Answers (2)

Mark Baker
Mark Baker

Reputation: 212412

The cos() and sin() functions expect the argument in radians, not in degrees.

Use the deg2rad() function to convert

EDIT

CODE:

function positionX($numItems,$thisNum){
  $alpha = 360/$numItems; // angle between the elements
  $r = 1000; // radius
  $angle = $alpha * $thisNum; // angle for N element
  $x = $r * cos(deg2rad($angle)); // X coordinates
  return $x;
}

function positionY($numItems,$thisNum){
  $alpha = 360/$numItems; // angle between the elements
  $r = 1000; // radius
  $angle = $alpha * $thisNum; // angle for N element
  $y = $r * sin(deg2rad($angle)); // Y coordinates
  return $y;
}

echo round(positionX(4,1))."<br>";
echo round(positionY(4,1))."<br><br>";

echo round(positionX(4,2))."<br>";
echo round(positionY(4,2))."<br><br>";

echo round(positionX(4,3))."<br>";
echo round(positionY(4,3))."<br><br>";

echo round(positionX(4,4))."<br>";
echo round(positionY(4,4))."<br><br>";

RESULTS:

0
1000

-1000
0

-0
-1000

1000
-0

Upvotes: 2

toxicate20
toxicate20

Reputation: 5410

Thats because you are not using radiants in your sin() and cos() functions. You need to convert angels into radiants. Look at the function description of sin(), there you find that the arg is in radiants.

Reminder

1° = 2 PI / 360;

Edit

I can't seem to find the error in your code, try this one instead

function($radius, $points, $pointToFind) {

 $angle = 360 / $points * 2 * pi(); //angle in radiants

 $x = $radius * cos($angle * $pointToFind);
 $y = $radius * sin($angle * $pointToFind);

}

Upvotes: 2

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