Convert bearing from degrees to direction

[ocon]

I have many bearings that I would like to convert into directions.

Is there a better way to see if a number falls within certain ranges?

if($bearing>=0 && $bearing>22.5) $direction="N";
else if($bearing>=22.5 && $bearing>67.5) $direction="NE";
else if($bearing>=67.5 && $bearing>112.5) $direction="E";
else if($bearing>=112.5 && $bearing>157.5) $direction="SE";
else if($bearing>=157.5 && $bearing>202.5) $direction="S";
else if($bearing>=202.5 && $bearing>247.5) $direction="SW";
else if($bearing>=247.5 && $bearing>292.5) $direction="W";
else if($bearing>=292.5 && $bearing>337.5) $direction="NW";
else $direction="N"

Thanks

[astupidname]

For the current task at hand, about the only other way I can think of at this time (only moderately prettier -eye of the beholder-, and very slightly quicker -approx .00025 seconds- ) :

$bearing = 321;

$cardinalDirections = array(
  'N' => array(337.5, 22.5),
  'NE' => array(22.5, 67.5),
  'E' => array(67.5, 112.5),
  'SE' => array(112.5, 157.5),
  'S' => array(157.5, 202.5),
  'SW' => array(202.5, 247.5),
  'W' => array(247.5, 292.5),
  'NW' => array(292.5, 337.5)
);

foreach ($cardinalDirections as $dir => $angles) {
  if ($bearing >= $angles[0] && $bearing < $angles[1]) {
    $direction = $dir;
    break;
  }
}

echo $direction;

[CyBerAliEn]

A more robust approach (if you are checking/working with multiple bearings)...

function getDirection($bearing)
{
 $cardinalDirections = array( 
  'N' => array(337.5, 22.5), 
  'NE' => array(22.5, 67.5), 
  'E' => array(67.5, 112.5), 
  'SE' => array(112.5, 157.5), 
  'S' => array(157.5, 202.5), 
  'SW' => array(202.5, 247.5), 
  'W' => array(247.5, 292.5), 
  'NW' => array(292.5, 337.5) 
 ); 
 
 foreach ($cardinalDirections as $dir => $angles)
 { 
  if ($bearing >= $angles[0] && $bearing < $angles[1])
  { 
   $direction = $dir; 
   break;
  } 
 } 
 return $direction;
}

code from astupidname, wrapped into a function

This way, you can call "getDirection()" and pass any bearing into it, and get the right direction out. IE:

$thisbearing = 321;
$thisdirection = getDirection($bearing);
//$thisdirection would equal 'NW'

[ocon]

I like the array function much better than a series of if/else statements, if not for aesthetics alone. I'm actually surprised that you have to run through a loop to detect if a number is within a range, it would seem there would be a more direct approach.

[eelixduppy]

Orrrr....if you want the fastest way I can think of, we just skip all comparisons and go right for the gold ;)

function getDir($b) { $dirs = array('N', 'NE', 'E', 'SE', 'S', 'SW', 'W', 'NW', 'N'); return $dirs[round($b/45)]; }

[Readie]

There's actually a more efficient way to do this. The above script carries on the loop after a match is made, so a for loop would most likely be more appropriate here:

function getDirection($bearing) {
  $cardinalDirections = array(
    array('N', 337.5, 22.5),
    array('NE', 22.5, 67.5),
    array('E', 67.5, 112.5),
    array('SE', 112.5, 157.5),
    array('S', 157.5, 202.5),
    array('SW', 202.5, 247.5),
    array('W', 247.5, 292.5),
    array('NW', 292.5, 337.5)
  );

  $count = count($cardinalDirections);

  for ($i = 0; $i < $count; $i++) {
    if ($bearing >= $cardinalDirections[$i][1] && $bearing < $cardinalDirections[$i][2]) {
      $direction = $cardinalDirections[$i][0];
      $i = $count;
    }
  }
  return $direction;
}

Should result in slightly faster run times.

EDIT:

Doh, just noticed the break; command in the above code. Oh well, for() has less overhead than foreach() anyways. Also, eelix posted as I was typing this :)

EDIT2:

Also... The array we've all blindely been using won't work.

array('N', 337.5, 22.5)

Need two N's:

array('N', 0, 22.5),
array('N', 337.5, 360)