Homework12_A

Add regression lines to your revised statistical application (parser + statistical/charting engine).

Code VB.Net

https://drive.google.com/file/d/1TFEmibUFSHRXVqiH9frzuWL0XIIPsjli/view?usp=sharing

To calculate regression line we use:

y = a + bx

Dim x_prec As Double = listOfBDataP(0).x1
        Dim y_dipPrec As Double = a + b * x_prec

        For Each d In listOfBDataP.Skip(1)
            Dim y_dipCurr As Double = a + b * d.x1
            Dim p_xPrec As Double = X_Viewport(x_prec, viewport, min_x, range_x)
            Dim p_yPrec As Double = Y_Viewport(y_dipPrec, viewport, min_y, range_y)
            Dim p_xCurr As Double = X_Viewport(d.x1, viewport, min_x, range_x)
            Dim p_yCurr As Double = Y_Viewport(y_dipCurr, viewport, min_y, range_y)
            gc.DrawLine(Pens.Red, New Point(p_xPrec, p_yPrec), New Point(p_xCurr, p_yCurr))
            x_prec = d.x1
            y_dipPrec = y_dipCurr
        Next

where

b = COV(X,Y)/variance
a = y – bx
(y and x are the average of Y and X value)

Remember:

Variance

Covariance

  Dim sigma = calc_var()
        Dim b As Double = Calc_cov() / sigma
        Dim a As Double = current_onlineMeanY - b * current_onlineMeanX

  Public Function Calc_cov() As Double
        Dim sum As Double
        Dim n As Double = listOfBDataP.Count
        For Each d In listOfBDataP
            sum += d.x1 * d.x2
        Next
        Return (sum - n * current_onlineMeanX * current_onlineMeanY) / (n - 1)
    End Function

    Public Function Calc_var() As Double
        Dim sigma As Double
        For Each d In listOfBDataP
            sigma += Math.Pow((d.x1 - current_onlineMeanX), 2)
        Next

        Return sigma / (listOfBDataP.Count - 1)
    End Function

https://www.webtutordimatematica.it/materie/statistica-e-probabilita/modelli-di-regressione/regressione-lineare-semplice/calcolo-parametri-retta-regressione