need help to code simpson 3/8 rule

[shm_yli]

i ask a for a help in this simpson 3/8 rule, in the past few days, and i cant really solve it, because in my assignment i need to show the vba code on how to compute my given, this is my given :

x | 0 | 20| 40 |60 |80 |100 |120|
y| 0 |7.4 |11.8 |15.2 |15| 9.2 |0.2|
h= 20 n= 6 segments

someone answered me but, i don't really get it, so i'm asking again for help again in this, on how i can code this in vba.

 

[Snakehips]

I'd never heard of Simpsons 3/8 rule until I read this. However, here is code that I think is manipulating your data correctly?
I have output the various elements for illustrative purposes.

MRXLMAY21.xlsm
	A	B	C	D	E	F	G	H	I	J
1
2	x	x		0	20	40	60	80	100	120
3	y = f(x)	y		0	7.4	11.8	15.2	15	9.2	0.2
4
5	Low Limit x	a		0
6	High Limit x	b		120
7	n Intervals	n		6
8	Increment h	h		20
9
10	Simpson's 3/8 Approximation
11	Simpson Sum Multiple
12	Simpson sum	161
13	Simpson 3h/8 Multiplier	7.5
14
15	Result	1206
16
BarCodes

Sub Simpsons()
Dim Rngx As Range
Dim Rngy As Range
Dim a, b, c, n, h
Dim SSum, SMult, LastCol
Dim Result

'Assume data is in Rows 2 & 3 starting column D
LastCol = Cells(2, Cells.Columns.Count).End(xlToLeft).Column

'data range
Set Rngx = Range(Cells(2, 4), Cells(2, LastCol))
Set Rngy = Range(Cells(3, 4), Cells(3, LastCol))

'intervals n
n = Rngx.Columns.Count - 1
If Not n Mod 3 = 0 Then
    MsgBox "Intervals 'n' MUST be a multiple of 3.  Please check your data and try again."
    Exit Sub
End If

'a = low x   b = High x
a = Rngx(1, 1)
b = Rngx(1, LastCol - 3)

'increment h
h = (b - a) / n

'Simpson sum elements for y as F(x) 0 to n
'Low and high limit values
SSum = Rngy(1, 1) + Rngy(1, LastCol - 3)

'intermediate elements attracting multiples
For c = 1 To LastCol - 5
    If c Mod 3 = 0 Then
        SSum = SSum + 2 * Rngy(1, c + 1)   'Elements with multiple 2
    Else
        SSum = SSum + 3 * Rngy(1, c + 1)    'Elements with multiple 3
    End If

Next c

'Calculate the overall multiplier
SMult = 3 / 8 * h

Result = SMult * SSum

'Illustrate
Range("D5") = a
Range("D6") = b
Range("D7") = n
Range("D8") = h

Range("B12") = SSum
Range("B13") = SMult

Range("B15") = Result

End Sub

Hope that helps.

 

[shm_yli]

I'd never heard of Simpsons 3/8 rule until I read this. However, here is code that I think is manipulating your data correctly?
I have output the various elements for illustrative purposes.

MRXLMAY21.xlsm
	A	B	C	D	E	F	G	H	I	J
1
2	x	x		0	20	40	60	80	100	120
3	y = f(x)	y		0	7.4	11.8	15.2	15	9.2	0.2
4
5	Low Limit x	a		0
6	High Limit x	b		120
7	n Intervals	n		6
8	Increment h	h		20
9
10	Simpson's 3/8 Approximation
11	Simpson Sum Multiple
12	Simpson sum	161
13	Simpson 3h/8 Multiplier	7.5
14
15	Result	1206
16
BarCodes

Sub Simpsons()
Dim Rngx As Range
Dim Rngy As Range
Dim a, b, c, n, h
Dim SSum, SMult, LastCol
Dim Result

'Assume data is in Rows 2 & 3 starting column D
LastCol = Cells(2, Cells.Columns.Count).End(xlToLeft).Column

'data range
Set Rngx = Range(Cells(2, 4), Cells(2, LastCol))
Set Rngy = Range(Cells(3, 4), Cells(3, LastCol))

'intervals n
n = Rngx.Columns.Count - 1
If Not n Mod 3 = 0 Then
    MsgBox "Intervals 'n' MUST be a multiple of 3.  Please check your data and try again."
    Exit Sub
End If

'a = low x   b = High x
a = Rngx(1, 1)
b = Rngx(1, LastCol - 3)

'increment h
h = (b - a) / n

'Simpson sum elements for y as F(x) 0 to n
'Low and high limit values
SSum = Rngy(1, 1) + Rngy(1, LastCol - 3)

'intermediate elements attracting multiples
For c = 1 To LastCol - 5
    If c Mod 3 = 0 Then
        SSum = SSum + 2 * Rngy(1, c + 1)   'Elements with multiple 2
    Else
        SSum = SSum + 3 * Rngy(1, c + 1)    'Elements with multiple 3
    End If

Next c

'Calculate the overall multiplier
SMult = 3 / 8 * h

Result = SMult * SSum

'Illustrate
Range("D5") = a
Range("D6") = b
Range("D7") = n
Range("D8") = h

Range("B12") = SSum
Range("B13") = SMult

Range("B15") = Result

End Sub

Hope that helps.

uhm. I copy paste this, and i get this msgbox "Intervals 'n' MUST be a multiple of 3. Please check your data and try again." i don't know if i still need to input some data or not.. and im asking if it is really smult = 3 / 8 * h or smult = 3 * h / 8 ??

thanks for answering my question.

 

[Snakehips]

uhm. I copy paste this, and i get this msgbox "Intervals 'n' MUST be a multiple of 3. Please check your data and try again." i don't know if i still need to input some data or not.. and im asking if it is really smult = 3 / 8 * h or smult = 3 * h / 8 ??

thanks for answering my question.

Then I assume that you have data in row 2 to the right of column J?
The original code was looking to be able to find variable number of columns. I have edited so that LastCol is now fixed at 10 for colum J.
3/8*h or 3*h/8, mathematically the same. I have however changed it.

Sub Simpsons()
Dim Rngx As Range
Dim Rngy As Range
Dim a, b, c, n, h
Dim SSum, SMult, LastCol
Dim Result

'Assume data is in Rows 2 & 3 starting column D

'In this instance data range is fixed D2:J3 so
LastCol = 10  'To limit to column J
'data range
Set Rngx = Range(Cells(2, 4), Cells(2, LastCol))
Set Rngy = Range(Cells(3, 4), Cells(3, LastCol))

'intervals n
n = Rngx.Columns.Count - 1
If Not n Mod 3 = 0 Then
    MsgBox "Intervals 'n' MUST be a multiple of 3.  Please check your data and try again."
    Exit Sub
End If

'a = low x   b = High x
a = Rngx(1, 1)
b = Rngx(1, LastCol - 3)

'increment h
h = (b - a) / n

'Simpson sum elements for y as F(x) 0 to n
'Low and high limit values
SSum = Rngy(1, 1) + Rngy(1, LastCol - 3)

'intermediate elements attracting multiples
For c = 1 To LastCol - 5
    If c Mod 3 = 0 Then
        SSum = SSum + 2 * Rngy(1, c + 1)   'Elements with multiple 2
    Else
        SSum = SSum + 3 * Rngy(1, c + 1)    'Elements with multiple 3
    End If

Next c

'Calculate the overall multiplier
SMult = 3 * h / 8

Result = SMult * SSum

'Illustrate
Range("D5") = a
Range("D6") = b
Range("D7") = n
Range("D8") = h

Range("B12") = SSum
Range("B13") = SMult

Range("B15") = Result

End Sub