func gradDecent(X [][]float64, y []float64, iterations int, alpha float64) []float64 {
theta := []float64{0.0, 0.0}
num := len(X)
feanum := len(X[0])
for iter := 0; iter < iterations; iter++ {
theta_update := []float64{0.0, 0.0}
for i := 0; i < num; i++ {
diff := utils.MultiplyVectors(X[i], theta) - y[i]
for f := 0; f < feanum; f++ {
theta_update[f] = theta_update[f] + diff*X[i][f]
}
}
for f := 0; f < feanum; f++ {
theta[f] = theta[f] - alpha*theta_update[f]/float64(num)
}
//fmt.Printf("iteration %d: cost=%f\n", iter, cost(X, y, theta))
}
return theta
}
func cost(X [][]float64, y []float64, theta []float64) float64 {
var J float64
num := len(X)
for i := 0; i < num; i++ {
diff := utils.MultiplyVectors(X[i], theta) - y[i]
J = J + diff*diff
}
return J / (float64(num) * 2)
}