I need to use simple exponential smoothing method to find a forecast for the past 3 years and next year. I cannot use MySQL, just php.
I am new at this and have no idea where to start.
*For those of you that don't know what exponential smoothing is, it is basically the following formula:
New forecast=(alpha)(Current demand) + (1-alpha)(Last Forecast)

alpha=0.2

Below is the data given.
Month 2009 2010 2011
Jan. 260 270 240
Feb. 220 210 250
Mar. 270 260 250
Apr. 300 280 260
May 269 259 225
June 271 280 257
July 240 220 230
Aug. 234 240 250
Sept. 220 240 230
Oct. 240 250 244
Nov. 262 271 257
Dec. 255 260 25

I would appreciate any help!
Thanks

    [man]array_reduce[/man] can apply a given function to an array element and the result of the previous application of the function. Assuming all the data points are in a single array $demands...

    $alpha = 0.2;
$initial_demand = array_shift($demands); // To start the reduction process off
$final_forecast = array_reduce($demands, function($last_forecast, $current_demand)use($alpha)
{
	return $alpha * $current_demand + (1 - $alpha) * $last_forecast;
}, $initial_demand);

      Are you sure that your function inside of array_reduce is right? I cannot make it work.

      Thanks for your time and help!

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