A Linear Regression Model in Solidity.

LinearModel.sol

pragma solidity ^0.4.9;

library Math {

    function mul (uint a, uint b, uint decimals) internal constant returns (uint) {
        return a*b/10**decimals;
    }
    
    function div (uint a, uint b, uint decimals) internal constant returns (uint) {
        return a*10**decimals/b;
    }
    
    function sqr(uint a, uint decimals) internal constant returns (uint) {
        return mul(a,a, decimals);
    }
}

contract LinearModel {

    event Push(address indexed from, uint x, uint y);
    event Update(address indexed from, uint w0, uint w1);

    
    uint[] public xtrain;
    uint[] public ytrain;
    uint[] public weights;
    uint public decimals;
    uint public error;
    uint public alpha;
    uint public iterations;

    function LinearModel(
        uint _decimals,
        uint _alpha,
        uint _iterations)
    {
        alpha = _alpha;
        decimals = _decimals;
        iterations = _iterations;
        weights = [10**decimals, 10**decimals];
    }
    
    function mul (uint a, uint b) returns (uint) {
        return Math.mul(a, b, decimals);
    }
    
    function div (uint a, uint b) returns (uint) {
        return Math.div(a, b, decimals);
    }

    
    function update () {

        for (var i = 0 ; i < xtrain.length; i++) {
            weights[0] -= Math.mul(Math.mul(200,alpha, decimals), estimate(xtrain[i]) - ytrain[i], decimals);
            weights[1] -= Math.mul(Math.mul(200, alpha, decimals), Math.mul(xtrain[i], (estimate(xtrain[i]) - ytrain[i]), decimals), decimals);
        }
        
        Update(msg.sender, weights[0], weights[1]);
    }

    function objective () returns (uint) {
        error = 0;
        for (var i = 0 ; i < xtrain.length; i++) {
            error += Math.sqr(estimate(xtrain[i]) - ytrain[i], decimals);
       }
        return error;
    }

    function estimate(uint x) constant returns(uint) {
        return Math.mul(weights[1],x, decimals) + weights[0];
    }
    
    function push(uint x, uint y) {
        xtrain.push(x);
        ytrain.push(y);
        Push(msg.sender,x,y);
    }

}