In a collection, how to create a column where the values should be: multiply a percentage in this item by a the number in the same column but from the item before.

[PowerGirl]

Hello everyone! I really, really need your help.

I need to calculate the total annual spend and the net present value for different projects. For that I have the following information in a table (sample info): 

Annual average volume   4000

Program life time in years    8

Cost reductions    3% in 3 years 2% in 2 years

Piece price 1.50 

The Rate% for the Present value calculation will be given in an input field in the app

I attached the table I need to create/simulate to be able to perform these calculations in excel. The explanation is as follows:

1. First I need to create a table with number of items from 0 to program life time in years . I store an index in the first column. 

2. For column 2 I need to transform the text in the column "Cost reductions" to a column stating the year 0 no cost  reductions, the next three years a reduction of 3% and the next 2 years a reduction of 2%

3. For column 3 I need to calculate the piece price for each year =Piece price of the previous year * (1-cost reduction of this year) (for the year 0 the piece price will be the one given in the item)

4. For the Total Spend column I need to multiply the calculated piece price of this year * annual average volume. The sum of this column will give me the Total Annual spend that I am looking for.

5. For the Present Value column I need to divide the total spend / (1-rate%)^ThisItem.year (the first column). The sum of this column will give me the Present Value

Until now I have created a collection as follows:

ForAll(Sequence(Value(Last(FirstN(Split(ThisItem.CostReduction, " "),3)).Result),1),Collect(Reduction1,{ReducPercentage:Last(FirstN(Split(ThisItem.CostReduction, " "),1)).Result,AnnualVol:LookUp(QBOM,QBOMIDinQBOM=ThisItem.QBOMIDinCBD1).TotalAnnualAvgCmpVolume,Index:CountRows(Reduction1)+1,PiecePrice:Left(Label64_1.Text,Find(" ",Label64_1.Text)),Spend:0}));
ForAll(Sequence(Value(Last(FirstN(Split(ThisItem.CostReduction, " "),7)).Result),1),Collect(Reduction2,{ReducPercentage:Last(FirstN(Split(ThisItem.CostReduction, " "),5)).Result,AnnualVol:LookUp(QBOM,QBOMIDinQBOM=ThisItem.QBOMIDinCBD1).TotalAnnualAvgCmpVolume,Index:CountRows(Reduction2)+CountRows(Reduction1)+1,PiecePrice:Left(Label64_1.Text,Find(" ",Label64_1.Text)),Spend:0}));
ForAll(Sequence(Value(Last(FirstN(Split(ThisItem.CostReduction, " "),11)).Result),1),Collect(Reduction3,{ReducPercentage:Last(FirstN(Split(ThisItem.CostReduction, " "),9)).Result,AnnualVol:LookUp(QBOM,QBOMIDinQBOM=ThisItem.QBOMIDinCBD1).TotalAnnualAvgCmpVolume,Index:CountRows(Reduction3)+CountRows(Reduction2)+CountRows(Reduction1)+1,PiecePrice:Left(Label64_1.Text,Find(" ",Label64_1.Text)),Spend:0}));
ForAll(Sequence(Value(Last(FirstN(Split(ThisItem.CostReduction, " "),15)).Result),1),Collect(Reduction4,{ReducPercentage:Last(FirstN(Split(ThisItem.CostReduction, " "),13)).Result,AnnualVol:LookUp(QBOM,QBOMIDinQBOM=ThisItem.QBOMIDinCBD1).TotalAnnualAvgCmpVolume,Index:CountRows(Reduction4)+CountRows(Reduction3)+CountRows(Reduction2)+CountRows(Reduction1)+1,PiecePrice:Left(Label64_1.Text,Find(" ",Label64_1.Text)),Spend:0}));
ClearCollect(Reduction,Reduction1,Reduction2,Reduction3,Reduction4); Clear(Reduction1);Clear(Reduction2);Clear(Reduction3);Clear(Reduction4);

as you can see the Piece Price the annual spend are not yet calculated. 

My questions:

Is there a better way to get the cost reductions into the collection (maybe dynamically)?

How can I create the column piece price? (I have tried with For All, Sequence, Patch, ThisRecord.Index-1 but I can not find the right combination and I can not patch in the same source as the for all) 

Is there a way to make a For All inside of a For All to make the calculation of the Total Annual Spend and the Present Value without creating a collection or how would you recommend me to do these calculations? 

Every help is welcome!

[RandyHayes]

@PowerGirl 

Actually, I pretty much understood where you were trying to get to.  @poweractivate there was an example shown in the first post that provides a clear enough example.  The only reasons for my questioning was that where @PowerGirl was on the particular problem being experienced was that it was FAR from the actual results expected.  In the first posting it was how to create a table on the given data.  That is simple enough, the challenge is that there are other mitigating aspects of the scenario that would apply to the overall solution (i.e. the Cost Reduction string).

Anyway, @PowerGirl I have this on my schedule to give you a good working solution.  It is not a trivial problem to solve as you have several factors in your example that I saw none of it being accounted for in your original formula.  Things like the fact that this a compounded amortization calculation with variable period rates.  Again, not a trivial formula.

I've been a little busy the past several days, so I will most certainly circle back on this and provided you something that you do not need to embed PowerBI or alter your datasource.

[PowerGirl]

Thank you @RandyHayes , I am looking forward to your proposed solution. Like you mention, it is not a trivial formula. 

[RandyHayes]

@PowerGirl 

Me too! 😉  Actually, I have the formula worked out except for the final amortization value.  Didn't get as much time to review it that I thought today.  I will get that last value working and post a formula for you tomorrow.

[RandyHayes · Accepted solution]

@PowerGirl 

Okay...I got a chance to go over this some more.  

So, it's a relatively complex formula as you have multiple aspects of variation going on why calculating on each.

In my sample setup, I have 5 TextInput controls.  One for the Annual Volume, one for the Program Years, one for the Cost Reduction formula, one for the Piece Price and one for the Rate.

Unfortunately, doing all of this without a collection is not possible (as I had hoped we could eliminate) because we (during the calculation) need to refer back to a prior value while at the same time generating a new prior value.  The only way I know to do this is with the collection as you can add a record and refer (Lookup) at the same time on the same collection.

I have the formula below on a Button and then have Two labels on my sample setup.

One label has a Text property of : finalAmortResult.AnnualSpendTotal

and One has a Text property of :  finalAmortResult.AnnualSpendAmortization

I did not do any rounding on the final numbers because I found that your example table did calculations on NON-Rounded numbers and that was significant.  

When the final numbers are rounded, they are off by $0.01.  Since I don't know the original formulas you had in your spreadsheet, I would assume there was something significant there for rounding. 

Based on the sample you provided, the formula returns the exact numbers you highlighted as what you need.  The formula is flexible to allow for expansion of the Cost Reduction formula as we mentioned in prior posts - as long as they observe the <percentage> in <X Years> format.

And...here is the formula.  I commented most of it as you might not be familiar with all of the aspects of it.

Clear(colAmort);

// At the Outer Level we are defining scope variables for input the the formula.  The controls in this With should be changed to reflect controls in the app
With({_CostReductionString: txtCostReduction.Text,
      _years: Value(txtYearsInSchedule.Text),
      _piecePrice: Value(txtPiecePrice.Text),
      _pieceQuantity: Value(txtPieceAmount.Text),
      _annualSpend: 1+(Value(txtAnnualSpend.Text)/100)},
    // First outer level in With - define a table of periods, there will be one record for each rate change and this scope variable will serve as the primary table for the final calculation
    With({_periods: 
        // In this With (2nd outer level) - define the series for each rate change period.  This will define the starting values, percentage rates, and start and end 
        With({series:
            // Perform a regular expression on the cost reduction series and gather up to 4 years of percentage rates 
            // (note: regex can be expanded for more years as needed)
            // all of the Match information will be in _cr table
            With({_cr:Match(_CostReductionString,  
                  "^(?:(?<p1>\d+)%)?\D*(?:(?<years1>\d+))?\D*(?:(?<p2>\d+)%)?\D*(?:(?<years2>\d+))?\D*(?:(?<p3>\d+)%)?\D*(?:(?<years3>\d+))?\D*(?:(?<p4>\d+)%)?\D*(?:(?<years4>\d+))?")},
                // Create a table of records with information from the matches.  
                // Each record will have the Period sequential value, the Sequence Number, the percent from the cost reduction string and the years from the string.
                // Filter out empty years
                Filter(
                    // note: Sequence - half of the count of matches (as each has a percent and a year(s)), start at 1, skip every other number
                    ForAll(Sequence(CountRows(_cr.SubMatches)/2, 1, 2),
                        If(!IsBlank(Last(FirstN(_cr.SubMatches, Value)).Value),
                            {Period: Value,
                             Seq: (Value+1)/2,
                             Percent: Value(Last(FirstN(_cr.SubMatches, Value)).Value),
                             years: Value(Last(FirstN(_cr.SubMatches, Value+1)).Value)
                            }
                        )
                    ),
                    years>0
                )
           )},

            // Create the series table.
            AddColumns(
                // create table from the sequence of all the series items (from the _cr).  
                // Adding two records to the series - one for starting period and one for ending period.  
                // It is assumed that year 0 is always the starting year with NO percentage change.
                // Start sequence at zero for year zero
                ForAll(Sequence(CountRows(series)+2,0),
                    // define a series year scope variable to calculate the starting year of the period
                    // get the sum of the prior period years and subtract out the years for the current period (add one to set bound)
                    With({sy:Sum(Filter(series, Seq<=Value), years) - Sum(Filter(series, Seq=Value), years)+1},
                       // Create record with sequential period number, start and end year of period, percent rate during period and starting Value (only for year 0)
                       {period:Value, 
                        start: If(Value=0, 0, sy), 
                        end: If(Value=0, 0, If(Value>Last(series).Seq, _years,  sy + LookUp(series, Seq=Value, years)-1)), 
                        pcnt: 1-(Coalesce(LookUp(series, Seq=Value, Percent),0)/100),
                        startValue: If(Value=0, _pieceQuantity * _piecePrice, 0),
                        amortRate: If(Value=0, 1, _annualSpend)
                       }
                    )
                ),
                // add a span helper column
                "Span", end-start+1
            )
        )},  //end of _period definition


        // throw away loop - loop through all the _periods in sequence. 
        ForAll(Sequence(CountRows(_periods)),
            // Grab the period record that corresponds to the current sequence
            With({_periodRec: Last(FirstN(_periods, Value))},
                // Grab the prior sequence value from the prior record of the collection colAmort we are building.
                // If we are at 0 (the year that holds the starting value) use that startValue from the current period record (it will be year 0)
                With({_priorValue: If(_periodRec.startValue=0, Last(FirstN(colAmort, CountRows(colAmort))).EndValue, _periodRec.startValue)},
                    // Preform the calculations on each item in the sequence for the amounts
                    With({_spanCalculations: ForAll(Sequence(_periodRec.Span), {seq:Value, amt:_priorValue * (_periodRec.pcnt^Value)})},
                        // Collect a new record with the main calculations
                        Collect(colAmort,
                            {   
                            // Total value for the entire period
                            // Sum all of the amortized values for each year in the current period based on the period percentage and the opening value
                            // Amortization formula is : value * (percentage ^ YearNumber)
                            PeriodTotal: Sum(_spanCalculations, amt), // Value),
                            // Calculate the ending amortized value (used for the next period)
                            EndValue: _priorValue * (_periodRec.pcnt^_periodRec.Span),
                            // Calculate the amortized values based on the period amounts, adjusting for the year in the span
                            AmortTotal: Sum(ForAll(_spanCalculations, amt / (_periodRec.amortRate ^ (seq + _periodRec.start - 1) )), Value)
                            }
                        )
                    )
                )
            )
        )    
    );

);

    // For convienience - a final record:
    Set(
    finalAmortResult, 
        {AnnualSpendTotal: Sum(colAmort, PeriodTotal),
         AnnualSpendAmortization: Sum(colAmort, AmortTotal)
        }
    )

I hope this is helpful for you.  Enjoy!!

[PowerGirl]

Wow, thank you very much for your time and for the formula. I will try it and let you know my questions/results.

[PowerGirl]

@RandyHayes 

I think I have easier questions this time. I tried your amazing formula and here are my questions:

1. I have evaluated 5 examples in the app with your formula and in the excel worksheet and I get all the same results except for example 2 (please see attachment). Might it be because the first 3 years are 0% reduction? I can not find the reason.

2. I want to compare the resulting Annual Spend Total and Annual Spend Amortization of different items in a gallery. Should I add this formula in an "add columns" for the collection I created? Or where should I perform this formula for it to calculate and display the values of the selected items? (I added a button in the gallery and two text labels to show the result, but it shows the same result in every item. How can I show the result of each separate item?)

[RandyHayes]

@PowerGirl 

Glad that we're making progress.  

Let me review this.  When I was putting that together I did only have the one sample, so I am anxious to see another and see how it fits.  I'm a little backlogged today, so let me check it over tomorrow.

[RandyHayes]

@PowerGirl 

Sorry to take so long...trying to work through the backlog.

Do you happen to have the full spreadsheet view of the ones that do not match (like you had in the first example)?

I have looked through the calculations in the app formula and they look fine based on my understanding of the formulas in the Excel.  So...that means I must have inferred the wrong formula from the Excel.  If you have something like that, I believe that would help a lot.

[PowerGirl]

@RandyHayes 

no problem, I appreciate your help. Please find attached the full spreadsheet view of the example 2. I believe it could be on the first 3 years 0% discount (that in reality they are 4 because the  year 0 is never considered) or maybe the program life time in years?

[RandyHayes]

@PowerGirl 

So I think there is an issue in your spreadsheet.  You show the the year 0 Annual spend as 918948.16.  From what I see in the column name, the annual spend is the year piece price multiplied by the annual volume.

You show 918948.16.  However 53558 * 17.16 = 919055.28

Is there a calculation that I am missing or is this a mistake in the spreadsheet?