# xlf EandA series

## Price to return

Code development version. This document provides some assignment solution ideas, presented here as an exercise.

## 0. Preliminary

### The EXERCISE - implement the following

**Part B Function procedures**

Insert a Code Module and name it *PartB*

**B.1** Write a private function procedure with the following specifications:

- Name:
*P2R*(an abbreviation of Price to Return) - Arguments:
- Compulsory - accepts a VBA array, with suitable name and type
- Optional - named
*Ret*(the default TRUE for log return, else FALSE for change in price)

- The function is only called from a VBA procedure, so the default value can be set in the function declaration line
- Argument 1 will always be an
*m x 1*column vector, with prices in ascending order, where*m*is the number of elements - The return value of "returns"" is an array of dimension
*(m - 1) x 1*

**B.2** Write a private sub procedure to test the *P2R* function. Pass the Close vector of the data test period to the function, and set the Optional argument to the default value. The test procedure writes the minimum, maximum and count statistics to the Immediate Window.

**B.3** Write a User Defined Function (UDF) procedure with the following specifications:

- Name:
*Price2Return*(an abbreviation of Price to Return) - Arguments:
- Compulsory - accepts a Range object, with suitable name and type
- Optional - named
*Ret*(the default TRUE for log return, else FALSE for change in price) - Optional - named
*Asc*(the default TRUE for ascending date order data, else FALSE for descending date order data)

- The function is primarily designed to be called from Excel
- Argument 1 will always be an
*n x 1*column vector of prices, where*n*is the number of elements - The return value of "returns" is an array of dimension
*(n - 1) x 1*, suitable for output as an array (CSE) formula - Test the function on the worksheet. Name the test area
*TestP2R*

**B.4** Write a User Defined Function procedure named *ArrDim* to return the number of rows in a column vector. The function has one compulsory argument, named *Arr* of suitable type. The return value should accommodate the maximum row dimension of a worksheet.

## 1. Tasks

This is a __code development version__ - that describes a series of tasks with suggested coding solutions. Note: "The "Close vector of the data test period" (from point B.2) is set to 10 observations in this version.

### Task 1.1: P2R

Write a private function procedure with the following specifications:

- Name:
**P2R**(an abbreviation of Price to Return) - Arguments:
**Compulsory**- accepts a VBA array, with suitable name and type**Optional**- named**Ret**(the default TRUE for log return, else FALSE for change in price)

- The function is only called from a VBA procedure, so the default value can be set in the function declaration line
- Argument 1 will always be an
*m x 1*column vector, with prices in ascending order.*m*is the number of elements - The return value of returns is an array of dimension
*(m - 1) x 1*

**Code 1:**the

`P2R`

function interpretation of task 1.1
Option Explicit Option Base 1 '' === B.1 Private Function P2R(Price() As Double, Optional Ret As Variant = True) As Variant '' P2R: Price to return '' Price: compulsory - a VBA array '' Ret: optional - a Boolean. True (default) for log return '' False for delta price return Dim LB As Integer, UB As Integer Dim t As Integer Dim RetArray() As Double '' Dimension the return value array LB = LBound(Price) UB = UBound(Price) ReDim RetArray(LB + 1 To UB, 1) If Ret = True Then '' Log returns For t = 1 To UB RetArray(t, 1) = Log(Price(t) / Price(t - 1)) Next t Else '' Change in price For t = 1 To UB RetArray(t, 1) = (Price(t) - Price(t - 1)) / Price(t - 1) Next t End If P2R = RetArray End Function

**About Code 1**

**Line 6:****function procedure declaration**- Private function with 1. Compulsory argument, a VBA array (dynamic) named**Price**. 2. Optional argument named**Ret**as Variant with assigned default value equals True.

**• Price**array is dynamic but does not need an associated Redim statement, because**Price**inherits the dimension of the Caller procedure. Code 2 passes a 9 element array (P Double(0 to 9)), thus**Price()**array has Type(dimension) Double(0 to 9) - see figure 1 for details

**• Ret**is type Boolean therefore has default value False. The declaration`Ret As Boolean = True`

initializes the parameter with value True.**P2R**is a private function called from VBA. There is no need for setting optional arguments to non bold in an Excel Function Arguments dialog box (which requires type Variant), nor testing the optional value with VBA`IsMissing`

function**Lines 17 and 18:**determine the lower (LB) and upper (UB) index numbers of the**Price**array (assumed to the one dimensional). The example has LB = 0, and UB = 9 (see figure 1)**Line 19:****Dimension RetArray**- the dynamic array for the return values to (LB + 1 to UB) = (1 to 9). Add a second dimension to force column orientation. Option Base 1 was set a line 2, meaning**RetArray**is Double(1 to 9, 1 to 1) - see figure 1**Line 24:****Log returns**- convert the \(r_{log.t} = log (P_t/P_{t-1})\) formula to a VBA code equivalent with time sub scripts. t = 1 to 9 because the price series is in ascending date order**Line 29:****Change in price returns \(\Delta P\)**- convert the \(r_{delta.t} = (P_t - P_{t-1}) / P_{t-1}\) formula to a VBA code equivalent

**Fig 1: Array**details -

**Price**| Double(0 to 9),

**P2R**| Variant/Double(1 to 9, 1 to 1), and

**RetArray**| Double(1 to 9, 1 to 1) [Scroll to view]

**Figure 2:**Constructing the VBA**P**array in a worksheet

**Fig 2: Constructing the P array**column O: extract 8 digits; column P: the P elements; and column Q: the concatenated assignment statements [Scroll to view]

**Column O:**Use 8 digits from the price series`O5: =LEFT(D5,8)`

**Column P:**Construct the individual P elements using concatenation`P6: ="P(" & ROW()-4 & ")"`

**Column Q:**Construct the assignment statements`Q7: =P7&" = "&ROUND(O7,4)`

- Copy the region with the red frame, and Paste to the VBA code module

### Task 1.2: TestP2R

Write a private sub procedure to test the *P2R* function. Pass the Close vector of the data test period to the function, and set the Optional argument to the default value. The test procedure writes the minimum, maximum and count statistics to the Immediate Window.

**Code 2:**

`TestP2R`

macro
'' === B.2 Private Sub TestP2R() '' Pass a Close vector of prices to P2R '' Print selected stats to the Immediate Window Dim P(0 To 9) As Double Dim RVal() As Double Const dPlaces As String = "0.00000" ' ANZ.AX Close prices 1Jul2016 to 14Jul2016 P(0) = 23.95 P(1) = 23.75 P(2) = 23.4 P(3) = 22.96 P(4) = 23.06 P(5) = 23.12 P(6) = 23.92 P(7) = 24.2 P(8) = 24.5 P(9) = 24.75 '' Log returns RVal = P2R(P, True) '' Write selected stats to Immediate Window Debug.Print """RVal = P2R(P, True)"": " & Time With WorksheetFunction Debug.Print "Return - Min: " & Format(.Min(RVal), dPlaces) Debug.Print "Return - Max: " & Format(.Max(RVal), dPlaces) Debug.Print "RVal(" & LBound(RVal) & "): " & Format(RVal(LBound(RVal), 1), dPlaces) Debug.Print "RVal(" & UBound(RVal) & "): " & Format(RVal(UBound(RVal), 1), dPlaces) Debug.Print "Return - Count: " & .Count(RVal) & vbNewLine End With '' Log returns RVal = P2R(P) '' Write selected stats to Immediate Window Debug.Print """RVal = P2R(P)"": " & Time With WorksheetFunction Debug.Print "Return - Min: " & Format(.Min(RVal), dPlaces) Debug.Print "Return - Max: " & Format(.Max(RVal), dPlaces) Debug.Print "RVal(" & LBound(RVal) & "): " & Format(RVal(LBound(RVal), 1), dPlaces) Debug.Print "RVal(" & UBound(RVal) & "): " & Format(RVal(UBound(RVal), 1), dPlaces) Debug.Print "Return - Count: " & .Count(RVal) & vbNewLine End With '' Delta returns RVal = P2R(P, False) '' Write selected stats to Immediate Window Debug.Print """RVal = P2R(P, False)"": " & Time With WorksheetFunction Debug.Print "Return - Min: " & Format(.Min(RVal), dPlaces) Debug.Print "Return - Max: " & Format(.Max(RVal), dPlaces) Debug.Print "RVal(" & LBound(RVal) & "): " & Format(RVal(LBound(RVal), 1), dPlaces) Debug.Print "RVal(" & UBound(RVal) & "): " & Format(RVal(UBound(RVal), 1), dPlaces) Debug.Print "Return - Count: " & .Count(RVal) & vbNewLine End With End Sub

**About Code 2**

- Details of the
**P**and**RVal**arrays are shown in figure 3 - The remainder of the code is straight forward

**Fig 3: Array**details -

**RVal**| Double(1 to 9, 1 to 1) ,

**Price**| Double(0 to 9),

**P2R**| Variant/Double(1 to 9, 1 to 1), and RetArray Double (1 to 9, 1 to 1) [Scroll to view]

**lines 64, 78, and 89:**Pass arguments by position to the**P2R**function, and return the "return series" to the**RVal**array - see figure 3- The
**Immediate Window**view is shown in figure 4

**Fig 4: Immediate Window**- with three variations of the P2R function

### Task 1.3: Price2Return

Write a User Defined Function (UDF) procedure with the following specifications:

- Name:
**Price2Return**(an abbreviation of Price to Return) - Arguments:
**Compulsory**- accepts a Range object, with suitable name and type**Optional**- named**Ret**(the default TRUE for log return, else FALSE for change in price)**Optional**- named**Asc**(the default TRUE for ascending date order data, else FALSE for descending date order data)

- The function is primarily designed to be called from Excel
- Argument 1 will always be an
*m x 1*column vector, where*m*is the number of elements - The return value of "returns" is an array of dimension
*(m - 1) x 1*, suitable for output as an array (CSE) formula - Test the function on the worksheet. Name the test area TestP2R

**Price2Return and P2R are linked** - from the specifications it is obvious there is a strong similarity between the VBA **P2R** function and the WS **Price2Return** function. This suggests that **P2R** can be utilized by **Price2Return**

In addition, the **ArrDim** function can also be used in the **Price2Return** procedure.

This means that **Price2Return** can perform the ascending / descending order manipulation of the:

- Price vector, and
- Return vector

**P2R**and the return vector is then oriented to match the direction of the original price vector.

In code 3, the **Price2Return** function is a "wrapper" for the **P2R** function. This means that **P2R** is called by **Price2Return**. The function can be tested from the **TestPrice2Return** procedure in code 5.

**Code 3:**

`Price2Return`

function
'' === B.3 Public Function Price2Return(PriceV As Range, _ Optional Ret As Variant, _ Optional Asc As Variant) _ As Variant '' Price2Return: Price to return '' PriceV: compulsory - a column vector of prices '' Ret: optional - a Boolean. True (default) for log return '' False for delta price return '' Asc: optional - a Boolean. True (default) for prices in Ascending order of date '' False for prices in Descending order of date '' Returns an (m - 1) vector of returns '' User requires knowledge of return vectors to select correct target range for CSE output Dim inArray() As Double Dim RValue() As Double Dim Rtemp() As Double ' Dimension set by the P2R function return array Dim t As Integer Dim r As Integer If IsMissing(Ret) Then Ret = True If IsMissing(Asc) Then Asc = True r = ArrDim(PriceV) ReDim RValue(0 To r - 2, 1 To 1) ReDim inArray(0 To r - 1) If Asc Then For t = 0 To r - 1 inArray(t) = PriceV(t + 1, 1) Next t Else ' Reverse order of prices For t = 0 To r - 1 inArray(t) = PriceV(r - t, 1) Next t End If '' Calculate returns Rtemp = P2R(inArray, Ret) If Asc Then Price2Return = Rtemp Else ' Reverse order of returns For t = 0 To r - 2 RValue(t, 1) = Rtemp(r - t - 1, 1) Next t Price2Return = RValue End If End Function

**About Code 3**

**Lines 107 to 110****procedure declaration**- an Excel UDF with two optional arguments. Use the Optional keyword and type Variant. Default values are handled by the IsMissing functions in lines 125 and 126. The arguments will display in non bold font in the WS Function Arguments dialog box**Line 119**declare**inArray**as a dynamic array of type Double -**inArray**handles the sort order of the**PriceV**price vector**Line 120**declare**RValue**as a dynamic array of type Double -**RValue**handles the Reverse order returns if Rtemp is descending**Line 121**declare**Rtemp**as a dynamic array of type Double -**Rtemp**stores the Return vector from**P2R**with values in ascending or descending order**Line 128**pass the**PriceV**range to the**ArrDim**function. Returns the value`10`

**Line 129**dimension the dynamic array**RValue**to`Double(0 to 8, 1 to 1)`

**Line 130**dimension the dynamic array**inArray**to`Double(0 to 9)`

**Lines 132 to 135**assign the**PriceV**range values (in ascending order), using row and column index counters to the VBA array**inArray**

counter`t = 0 to r - 1 :: t = 0 to 9`

.**inArray**has base 0,**PriceV**has base 1

`inArray(t) = PriceV(t + 1, 1).Value :: inArray({0,1,...,8,9) = PriceV({1,2,...9,10}, 1)`

Note: a VBA array does not have a value property**Lines 138 to 140**assign the**PriceV**range values (in descending order), using row and column index counters to the VBA array**inArray**in reverse order, ascending, as required by the**P2R**function

counter`t = 0 to r - 1 :: t = 0 to 9`

`inArray(t) = PriceV(r - t, 1) :: inArray({0,1,...,8,9) = PriceV({10,9,...,2,1}, 1)`

**Line 144**call the**P2R**function and assign the return array to the non dimensioned array**Rtemp**. The assignment dimensions (ReDim's)**Rtemp**to`Double(1 to 9, 1 to 1)`

, the same as the source**P2R**(see figure 3)**Line 147**if prices are**Asc**ending then return the "return vector" to the Caller**Lines 150 to 152**if prices are**Desc**ending assign the**Rtemp**returns (in ascending order) as returned by the**P2R**function, to the VBA array**RValue**in reverse order, descending, to match the PriceV order

counter`For t = 0 To r - 2 :: t = 0 to 8`

`RValue(t, 1) = Rtemp(r - t - 1, 1) :: RValue({0,1,...,7,8) = Rtemp({9,8,...,2,1}, 1)`

### Task 1.4: ArrDim

Write a User Defined Function procedure named ArrDim to return the number of rows in a column vector. The function has one compulsory argument, named Arr of suitable type. The return value should accommodate the maximum row dimension of a worksheet.

**Code 4:**

`ArrDim`

function
'' === B.4 Function ArrDim(Arr As Range) As Variant ' A UDF called from Excel WS ' Count number of rows in column vector ' Returns #Ref error if Arr is not an m x 1 column - additional feature If Arr.Columns.Count > 1 Then ArrDim = CVErr(xlErrRef) Else ArrDim = Arr.Rows.Count End If End Function

**Code 5:**

`TestPrice2Return`

macro
'' Additional procedure '' Written in the spirit of code 2 Private Sub TestPrice2Return() Dim RVal() As Double Dim Prices As Range '' Place 1 of 2:: Uncomment / comment as required - Asc / Desc 'Set Prices = Range("PriceAsc") Set Prices = Range("PriceDes") RVal = Price2Return(PriceV:=Prices, Asc:=False) '' Place 2 of 2 :: Asc / Desc Stop End Sub

**Fig 6: xlf Animated worksheets**Price2Return as an array formula (CSE) - edit existing array formula [Scroll to view]

## 2. Discussion

As stated in section 1, this module is a __code development version__, so a number of points are available for discussion.

### Q1: Option Base 1 declaration

**Code 1 line 2**includes the declaration**Option Base 1**to set the default lower bound of arrays in the module, but array declarations at lines 19, 47, 129, and 130 explicitly include the lower and upper index number with the**To**keyword.- Is Option Base 1 required?
- In general, the use of
**Option Base 1**should be avoided. Instead, use the**To**keyword to explicitly set the lower and upper index numbers of each array dimension. The code can then be read without knowledge of the**Option Base**declaration. For example, code 3, lines 129 and 130. Pointing the way,**Option Base 1**serves no real purpose, and could be deleted. Line 19 should then be written as: - In this version, however,
**Option Base 1**is in the module declaration and its impact on the line 19 declaration statement of**RetArray**is examined next - The result of the declaration can be viewed in the Locals Window (Expression; Type), see figure 3, and repeated here for reference
- With
**Option Base 1**__set__

**RetArray****Double(1 to 9, 1 to 1)** - If
**Option Base 1**is__commented out__(equivalent to**Option Base 0**), then**RetArray**will be (Expression; Type)

**RetArray****Double(1 to 9, 0 to 1)** - In other words, removing the
**Option Base**declaration changes the size of the second dimension from one column to two columns - In this example there is no practical difference, because the population code at lines 24 and 29 includes index 1 for the second dimension
- You just end up with a vector of zeros in the second dimension index 0. See figure 7
- RValue is declared with a column range "1 To 1", why not simply use "1"?
- The
**RValue**declaration is in line 129 - The logic of the answer is the same as that for
**RetArray**above - Summary
- be consistent with Declaration statements involving array dimensions
- use the
**To**keyword to explicitly declare lower and upper bounds - avoid using
**Option Base**, but be aware of it with other code sources

**Code 1**

19

**ReDim**RetArray(LB + 1

**To**UB, 1) ' dimension 2: upper index only

**Code 2**

47

**Dim**P(0

**To**9) As Double

**Code 3**

129

**ReDim**RValue(0

**To**r - 2, 1

**To**1)

130

**ReDim**inArray(0

**To**r - 1)

**Code 1**

19

**ReDim**RetArray(LB + 1

**To**UB, 1

**To**1) ' dimension 2: indexed 1 to 1 (a single column)

**Code 1**

24 RetArray(t, 1) = Log(Price(t) / Price(t - 1))

29 RetArray(t, 1) = (Price(t) - Price(t - 1)) / Price(t - 1)

**Fig 7: Locals Window**- the RetArray with Option Base 0 has a dimension 2 lower index of 0

**Code 3**

129

**ReDim**RValue(0

**To**r - 2, 1

**To**1) ' The array dimension 2 has explicit upper and lower bounds

129

**ReDim**RValue(0

**To**r - 2, 1) ' With Option Base 1, this is equivalent to 1 To 1

129

**ReDim**RValue(0

**To**r - 2, 1) ' With Option Base 0, dimension 2 is 0 To 1

129

**ReDim**RValue(0

**To**r - 2, 0) ' With Option Base 0, dimension 2 is 0 To 0 (equivalent to 1 column)

Option Base 0 is the default and is usually omitted

In the absence of any compelling logic, the choice of base is simply the analysts preference

### Q2: Code 5 - ascending and descending?

- Code 5 you have two separate ranges - one for Price descending and one for Price ascending - what is the point of this. Isn't the Price2Return function in code 3 designed to intrinsically sort returns into ascending or descending from a single column vector range of prices (with direction set by Asc argument)?
- Code 5 is a sub procedure named
**TestPrice2Return**, and as the name suggests this is designed to test (the accuracy of) the**Price2Return**function by passing range objects:- There are two arguments, with four combinations
- Ascending :: Log
- Ascending :: Change
- Descending :: Log
- Descending :: Change

- Yes - the direction can be switched by the
**Asc**argument, but does it give the correct answer? - In figure 6, the return vectors for the four combinations are calculated. You can download the workbook to view columns H to N
- When
**TestPrice2Return**is set to (combination 3 above): - The
**RVal**array in the**Locals Window**can be compared to the WS function values - see figure 8 - This can be repeated for the other combinations, with the inclusion of the
**Ret**parameter - The final test is using the UDF
**Price2Return**on a WS - see figure 6

**Code 5**

185**Set**Prices = Range("PriceDes")

187 RVal = Price2Return(PriceV:=Prices, Asc:=False))

189 Stop

**Fig 8: Locals Window**- Price2Return ... [Scroll to view] - There are two arguments, with four combinations

- Thanks to Cosmo for comments
**Download**the Excel file for this module: xlf-price2return-v2.xlsm [30 KB]**Development platform:**Excel 2016 (64 bit) Office 365 ProPlus and VBA 7.1**Revised:**Thursday 8th of February 2018 - 08:29 AM, [Australian Eastern Time (AET)]