Question

Given a list of points, I need to achieve a simple linear regression on them. This part is quite easy and code examples can be found in a lot of places.

My problem is determining the regression factor (measuring how much the points fit on the line). How could I determine such a factor programmatically, using Lua?

Answer 1

e$ lua
Lua 5.1.4  Copyright (C) 1994-2008 Lua.org, PUC-Rio
> function calculate_MSE (points, slope, offset)
>>     local SE = 0
>>     local num_pts = 0
>>     for x,y in pairs(points) do
>>         local p = slope * x + offset
>>         local err = y - p
>>         SE = SE + err * err
>>         num_pts = num_pts + 1
>>     end
>>     return SE / num_pts
>> end
> return calculate_MSE({1, 2, 3}, 1, 0)                                                                                                             0> return calculate_MSE({1, 2, 3}, 1, 1)1> return calculate_MSE({1, 2, 3}, 2, 1)9.6666666666667>
0
> return calculate_MSE({1, 2, 3}, 1, 1)
1
> return calculate_MSE({1, 2, 3}, 2, 1)
9.6666666666667
>