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atan2

(PHP 4, PHP 5, PHP 7, PHP 8)

atan2两个参数的反正切

说明

atan2 ( float $y , float $x ) : float

本函数计算两个变量 xy 的反正切值。和计算 y / x 的反正切相似,只除了两个参数的符号是用来确定结果的象限之外。

本函数的结果为弧度,其值在 -PI 和 PI 之间(包括 -PI 和 PI)。

参数

y

Dividend parameter

x

Divisor parameter

返回值

xy 的反正切弧度值。

参见

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在线手册:中文 英文

5位用户评论

[#1] ▲2▼ mirellastitan@gmail.com [100%] (2017-06-21 20:09:26)

The russian translation for this article contains a translation error. Делитель and Делимое should be visa versa: Делимое is the dividend Делитель is the divisor Thank you in advance for fixing this issue. It's quite confusing

[#2] ▲-1▼ andyidol@gmail.com [43%] (2010-08-10 08:18:10)

This function will return degree by vertex coordinates in general trigonometrical coordinate system where zero is located at position (1, 0), 90' at (0, 1), 180' at (-1, 0) and so on. <?php

function GetDegree($x$y)
{
  
// we don't want to cause division by zero
  
if($x == 0$x 10000;
      
  
$deg rad2deg(atan(abs($y $x)));
      
  if(
$y >= 0$deg $x 180 $deg $deg;
  else        
$deg $x 180 $deg 360 $deg;
      
  return 
$deg;
      
}

?>

[#3] ▲7▼ fred.beck@rrd.com [65%] (2009-01-11 12:39:01)

<?php
/**
 *    Given an origin point of (0,0) and a destination point $x,$y
 *  somewhere on an axis grid, compass() determines the compass
 *  heading(direction) of the destination point from the origin
 *    
 *  HOWEVER, atan2(y,x)'s natural compass thinks east is north, 
 * 
 *  {135}-------{ 90}-------{45}
 *      | +-----[ +y]-----+ |  
 *      | |               | |  
 *      | |               | |  
 *  {180} [-x]  [0,0]  [+x] {0} <--------- North ?
 *      | |               | |  
 *      | |               | |  
 *      | +-----[ -y]-----+ | 
 * {-135}-------{-90}-------{-45}
 *
 *
 *    SO, we simply transpose the (y,x) parameters to atan2(x,y) 
 *     which will both rotate(left) and reflect(mirror) the compass. 
 *
 *  Which gives us this compass
 * 
 *  {-45}-------{ 0 }-------{45}
 *      | +-----[ +y]-----+ |  
 *      | |               | |  
 *      | |               | |  
 *  {-90} [-x]  [0,0]  [+x] {90}
 *      | |               | |  
 *      | |               | |  
 *      | +-----[ -y]-----+ | 
 * {-135}-------{180}-------{135}
 *
 *  FINALLY,` we check if param $x was indeed a negative number, 
 *  if so we simply add 360 to the negative angle returned by atan2() 
 *    
 */
function compass($x,$y)
    {
        if(
$x==AND $y==0){ return 0; } // ...or return 360
        
return ($x 0)
        ? 
rad2deg(atan2($x,$y))+360      // TRANSPOSED !! y,x params
        
rad2deg(atan2($x,$y)); 
    }
function 
polar($x,$y)
    {
        
$N = ($y>0)?'N':'';
        
$S = ($y<0)?'S':'';
        
$E = ($x>0)?'E':'';
        
$W = ($x<0)?'W':'';        
        return 
$N.$S.$E.$W;
    }
function 
show_compass($x,$y)
     {
         return 
'<BR>'
             
.polar($x,$y)
             .
' compass( x='.$x.', y='.$y.' )= '
             
.number_format(compass($x,$y),3).'&deg';
     }

echo 
show_compass(0,3);
echo 
show_compass(.06,3);
echo 
show_compass(3,3);
echo 
show_compass(3,.06);
echo 
show_compass(3,0);
echo 
show_compass(3,-.06);
echo 
show_compass(3,-3);
echo 
show_compass(.06,-3);
echo 
show_compass(0,-3);
echo 
show_compass(-.06,-3);
echo 
show_compass(-3,-3);
echo 
show_compass(-3,-.06);
echo 
show_compass(-3,0);
echo 
show_compass(-3,.06);
echo 
show_compass(-3,3);
echo 
show_compass(-.06,3);

/* RENDERS THIS

N compass( x=0, y=3 )= 0 °
NE compass( x=0.06, y=3 )= 1.14576283818 °
NE compass( x=3, y=3 )= 45 °
NE compass( x=3, y=0.06 )= 88.8542371618 °
E compass( x=3, y=0 )= 90 °
SE compass( x=3, y=-0.06 )= 91.1457628382 °
SE compass( x=3, y=-3 )= 135 °
SE compass( x=0.06, y=-3 )= 178.854237162 °
S compass( x=0, y=-3 )= 180 °
SW compass( x=-0.06, y=-3 )= 181.145762838 °
SW compass( x=-3, y=-3 )= 225 °
SW compass( x=-3, y=-0.06 )= 268.854237162 °
W compass( x=-3, y=0 )= 270 °
NW compass( x=-3, y=0.06 )= 271.145762838 °
NW compass( x=-3, y=3 )= 315 °
NW compass( x=-0.06, y=3 )= 358.854237162 °

*/

?>

[#4] ▲0▼ monte shaffer [50%] (2007-06-08 11:35:04)

Here is a function that will return a new point [Rotate around non-origin pivot point] (x,y) is current point (cx,cy) is pivot point to rotate =a= is angle in degrees $_rotation = 1; # -1 = counter, 1 = clockwise $_precision = 2; # two decimal places function returnRotatedPoint($x,$y,$cx,$cy,$a) { # http://mathforum.org/library/drmath/view/63184.html global $_rotation; # -1 = counter, 1 = clockwise global $_precision; # two decimal places // radius using distance formula $r = sqrt(pow(($x-$cx),2)+pow(($y-$cy),2)); // initial angle in relation to center $iA = $_rotation * rad2deg(atan2(($y-$cy),($x-$cx))); $nx = number_format($r * cos(deg2rad($_rotation * $a + $iA)),$_precision); $ny = number_format($r * sin(deg2rad($_rotation * $a + $iA)),$_precision); return array("x"=>$cx+$nx,"y"=>$cy+$ny); }

[#5] ▲12▼ reubs@idsdatanet.com [75%] (2003-05-23 13:01:59)

Just a note: PHP's atan2 function receives parameters in (y,x) and Excel receives it in (x,y) format. Just in case you are porting formulas across. :)