Euler method: Difference between revisions

=={{header|VBA}}==

{{trans|Phix}}<lang vb>Private Sub ivp_euler(f As String, y As Double, step As Integer, end_t As Integer)

Dim t As Integer

Debug.Print " Step "; step; ": ",

Do While t <= end_t

If t Mod 10 = 0 Then Debug.Print Format(y, "0.000"),

y = y + step * Application.Run(f, y)

t = t + step

Loop

Debug.Print

End Sub

Sub analytic()

Debug.Print " Time: ",

For t = 0 To 100 Step 10

Debug.Print " "; t,

Next t

Debug.Print

Debug.Print "Analytic: ",

For t = 0 To 100 Step 10

Debug.Print Format(20 + 80 * Exp(-0.07 * t), "0.000"),

Next t

Debug.Print

End Sub

Private Function cooling(temp As Double) As Double

cooling = -0.07 * (temp - 20)

End Function

Public Sub euler_method()

Dim r_cooling As String

r_cooling = "cooling"

analytic

ivp_euler r_cooling, 100, 2, 100

ivp_euler r_cooling, 100, 5, 100

ivp_euler r_cooling, 100, 10, 100

End Sub</lang>{{out}}

<pre> Time: 0 10 20 30 40 50 60 70 80 90 100

Analytic: 100,000 59,727 39,728 29,797 24,865 22,416 21,200 20,596 20,296 20,147 20,073

Step 2 : 100,000 57,634 37,704 28,328 23,918 21,843 20,867 20,408 20,192 20,090 20,042

Step 5 : 100,000 53,800 34,281 26,034 22,549 21,077 20,455 20,192 20,081 20,034 20,014

Step 10 : 100,000 44,000 27,200 22,160 20,648 20,194 20,058 20,017 20,005 20,002 20,000 </pre>