Replace Values Conditionals - excel

Question

I want to replace values based on certain conditions. I can do this for the values in a specific column but I am not sure how to convert the code to have it work for all values in a range of columns.
This is my code currently:
Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
ColumnNames = Table.ColumnNames(Source),
Step1 = Table.ReplaceValue(Source,
each[L1_Grade],
else if Text.Contains([L1_Grade], "A") then "Upper"
else if Text.Contains([L1_Grade], "B") then "Middle"
else if Text.Contains([L1_Grade], "C") then "Lower"
else if Text.Contains([L1_Grade], "NaN") then ""
else if Value.Is(Value.FromText([L1_Grade]), type number) then "Num"
else [L1_Grade], Replacer.ReplaceText, ColumnNames)
in
Step1
How do I modify my code so it works for any of the columns specified using ColumnNames? I am not sure what to replace [L1_Grade] with.

Answer 1

Assuming, you have such table:
Then you may use following code:
let
Source = Excel.CurrentWorkbook(){[Name = "Data"]}[Content],
replace = Table.ReplaceValue(
Source,
0,
0,
(a, b, c) =>
let
f = (x) => Text.Contains(a, x),
y = try Number.From(a) otherwise a
in
if y is number and not Number.IsNaN(y) then
"Num"
else if f("A") then
"Upper"
else if f("B") then
"Middle"
else if f("C") then
"Lower"
else if f("NaN") then
""
else
a,
Table.ColumnNames(Source)
)
in
replace
Some comments:
Of course, you may use different list of columns in the last argument of the function.
The code may be simplified, if numbers are always as type text and/or may be only single version of "NaN".
If the replacement logic should be case-sensitive - adjust this line:
f = (x) => Text.Contains(a,x,Comparer.OrdinalIgnoreCase),
But since "NaN" contains "a" letter, some other code changes are required.