blogs@bluerhinos.co.uk

Code Tags: PHP
I was working on a project that needed to list the Beaufort wind force. The first attempt was to do a lookup based function using the data here: http://en.wikipedia.org/wiki/Beaufort_scale

Attempt 1

php code:
function beaufort_scale($speed, $unit="m/s"){
 
    $units['m/s'] = 1;
    $units['kph'] = 1/3.6;
    $units['mph'] = 0.44704;
    $units['kts'] = 0.514444444;
 
    if(!in_array($unit,array_keys($units))){
        return "Error: couldn't recognise unit";
    }
 
    $speed *= $units[$unit];
 
    $scale = array(0.3,1.5,3.4,5.4,7.9,10.7,13.8,17.1,20.7,24.4,28.4,32.6,1000);
 
    foreach($scale as $key=>$val){
        if($speed <= $val) return $key;
    }
    return 'Error';
}

I then noticed on the wikipedia page the scale's empirical formula
so i thought i could improve the function ;)

v = 0.866 * B^3/2 (units m/s)

Attempt 2

php code:
function beaufort_scale($speed, $unit="m/s", $rnd=0){
 
   $units['m/s'] = 1;
   $units['kph'] = 1/3.6;
   $units['mph'] = 0.44704;
   $units['kts'] = 0.514444444;
 
   if(!in_array($unit,array_keys($units))){
      return "Error: couldn't recognise unit";
   }
 
   $speed *= $units[$unit];
 
   $scale = pow(($speed/0.836),(2/3));
 
   return round($scale,$rnd);
}

This one has the added ability of returning a decimal answer