The Date Where There Is Enough Supply To Satisfy Dem - excel

Question

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I am trying to come up with a solution to the following problem.
Problem:
In my dataset I have certain quantity of item in demand (need), and purchase orders that re-supply that item(Supply). I need to determine for each demand , what is the first date where we will have enough supply to fill the demand.
For example, if we look at our 1st demand, which require 5 units, according to the cumulative Sum column, 18/12/23 will be the first date when we would have enough qty supplied to satisfy the first demand. The problem appears when we have more the one demand for an item.
If we stay with same item What I would like to do is to update the cumulative Sum when we meet the enough quantity ( as cumulative Sum = cumulative Sum- qty(demand) or 6(cumulative supply)-5(demand) = 1 ) so the cumulative Sum for the next demand will be 100 +1 = 101 and not 100 + 6 = 106. Thereby we can simply rely on the cumulative Sum (updated) to retrieve the first date where we will have enough supply to fill the demand.
I'm not sure if something like this is possibly in Power Query but any help is greatly appreciated.
Hopefully that all makes sense. Thx.

Answer 1

Revised
In powerquery try this as code for Demand
let Source = Excel.CurrentWorkbook(){[Name="DemandDataRange"]}[Content],
#"SupplyGrouped Rows" = Table.Group(Supply, {"item"}, {{"data", each
let a = Table.AddIndexColumn( _ , "Index", 0, 1),
b=Table.AddColumn(a, "CumTotal", each List.Sum(List.FirstN(a[Qty],[Index]+1)))
in b, type table }}),
#"SupplyExpanded data" = Table.ExpandTableColumn(#"SupplyGrouped Rows", "data", { "Supply date", "CumTotal"}, {"Supply date", "CumTotal"}),
#"Grouped Rows" = Table.Group(Source, {"item"}, {{"data", each
let a= Table.AddIndexColumn(_, "Index", 0, 1),
b=Table.AddColumn(a, "CumTotal", each List.Sum(List.FirstN(a[Qty],[Index]+1)))
in b, type table }}),
#"Expanded data" = Table.ExpandTableColumn(#"Grouped Rows", "data", {"Qty", "Date", "Index", "CumTotal"}, {"Qty", "Date", "Index", "CumTotal"}),
x=Table.AddColumn(#"Expanded data","MaxDate",(i)=>try Table.SelectRows( #"SupplyExpanded data", each [item]=i[item] and [CumTotal]>=i[CumTotal] )[Supply date]{0} otherwise null, type date ),
#"Removed Columns" = Table.RemoveColumns(x,{"Index", "CumTotal"}),
#"Changed Type" = Table.TransformColumnTypes(#"Removed Columns",{{"Date", type date}})
in #"Changed Type"

Answer 2

Given my understanding of what you want for results, the following Power Query M code should return that.
If you just want to compare the total supply vs total demand, then only check the final entries instead of the first non-negative.
Read the code comments, statement names and explore the Applied Steps to understand the algorithm.
let
//Read in the data tables
//could have them in separate querries
Source = Excel.CurrentWorkbook(){[Name="Demand"]}[Content],
Demand = Table.TransformColumnTypes(Source,{{"item", type text}, {"Qty", Int64.Type}, {"Date", type date}}),
//make demand values negative
#"Transform Demand" = Table.TransformColumns(Demand,{"Qty", each _ * -1}),
Source2 = Excel.CurrentWorkbook(){[Name="Supply"]}[Content],
Supply = Table.TransformColumnTypes(Source2,{{"item", type text},{"Qty", Int64.Type},{"Supply date", type date}}),
#"Rename Supply Date Column" = Table.RenameColumns(Supply,{"Supply date","Date"}),
//Merge the tables and sort by Item and Date
Merge = Table.Combine({#"Rename Supply Date Column", #"Transform Demand"}),
#"Sorted Rows" = Table.Sort(Merge,{{"item", Order.Ascending}, {"Date", Order.Ascending}}),
//Group by Item
//Grouped running total to find first positive value
#"Grouped Rows" = Table.Group(#"Sorted Rows", {"item"}, {
{"First Date", (t)=> let
#"Running Total" = List.RemoveFirstN(List.Generate(
()=>[rt=t[Qty]{0}, idx=0],
each [idx]<Table.RowCount(t),
each [rt=[rt]+t[Qty]{[idx]+1}, idx=[idx]+1],
each [rt]),1),
#"First non-negative" = List.PositionOfAny(#"Running Total", List.Select(#"Running Total", each _ >=0), Occurrence.First)
in t[Date]{#"First non-negative"+1}, type date}})
in
#"Grouped Rows"
Supply
Demand
Results

Answer 3

I did this in Excel formula rather than using powerquery - there will be a powerquery equivalent but I'm not very fluent in DAX yet.
You need a helper column - could do without it but everything's much more readable if you have it.
In sheet Supply (2), cell E2, enter the formula:
=SUMIFS(Supply!B:B; Supply!C:C;"<=" & C2;Supply!A:A;A2)-SUMIFS(Dem!B:B;Dem!C:C;"<=" & C2;Dem!A:A;A2)
and copy downwards. This can be described as Total supply up to that date minus total demand up to that date. In some cases this will be negative (where there's more demand than supply).
Now you need to find the date of the first non-negative value for that.
First create a unique list of the items - I put it on the same sheet in the range G2:G6. Then in H2, the formula:
=MINIFS(C:C;A:A;G2;E:E;">=" & 0)
and copy downwards.