LOOP to Look up the value in M Query

[qsong]

Hi,

I have a following data table:

I need to create a column called FINAL VALUE with certain rules in the power query editor:

- The FINAL VALUE is created based on the COUNTRY
- If VALUE is greater than 100, then the previous value will be taken
- if the previous values (no previous value such as 202001) are all greater than 100, then 100

So the final table should look like:

I sort COUNTRY and DATE, and then I try to apply loop in M Query. As I am not familiar with the function in M query, I have hard time figuring out. I appreciate any help. Thank you.

[v-alq-msft · Accepted solution]

Hi, @qsong 

Based on your description, I created data to reproduce your scenario. The pbix file is attached in the end.

Table:

You may go to 'Query Editor'=>'Add Column'=>'Custom Column', input the following codes.

let
country=[Country],date=[Date],
tab = Table.SelectRows(
    #"Changed Type",
    each [Country]=country and [Date]<date and [Value]<100
)
in 
if Table.RowCount(tab)>0 
then 
   if [Value]>100 
   then Table.Max(tab,"Date")[Value]
   else [Value]
else 
if [Value]<100
      then [Value]
      else 100

Result:

Best Regards

Allan

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

[qsong]

Hi @v-alq-msft ,

You answer is very helpful. Thanks a lot.

Best, Qianru

[Fowmy]

Hi @v-alq-msft 

That is a neat solution!

I am very much interested in improving my M skills; can you direct me to some M language resources for deep learning of the language?

Thanks
Fowmy 

[ToddChitt]

If this was SQL I would say that you can JOIN the table to itself on something OTHER than an EQUAL JOIN.

SELECT * FROM MyTable AS A

INNER JOIN MyTable AS B

   ON A.Country = B.Country

  AND A.Date < B.Date

That would effectively get you every iteration of a Country/Date plus all previuos Dates.

Then a GROUP BY the A columns and take the MIN of B.Value

But we're not SQL, sorry.