Counting aggregated and then getting average - google-data-studio

Question

So, I am sure it's got to be simple, but, I cannot get Google Data Studio to provide an average of two aggregated columns. Example:
+----------+----------+
| Column 1 | Column 2 |
+----------+----------+
| A | TRUE |
| A | FALSE |
| B | TRUE |
| C | FALSE |
| A | TRUE |
| C | TRUE |
| B | FALSE |
| B | TRUE |
+----------+----------+
How can you get a count of the total value of A in Column 1 and divide it by the total number of TRUE in Column 2? I have tried Count(Column 1)/Count (Column 2) but it gives me the totals for the other values as well.
I have tried creating a new field with a CASE statement, but there is an error when trying to divide the two resulting CASE WHEN values:
CASE
WHEN Column 1 = A THEN 1
ELSE 0
END

Answer 1

The below shows two approaches of achieving the required calculation:
Approach 1: Ratio Metrics
Using Scorecards, Filters and Ratio Metrics:
1) Column 1 (A) Scorecard
- Add a Scorecard;
- Drag and Drop the field Column 1 onto the Metric field and change the aggregation to COUNT;
- Create and apply the Filter: Include Column 1 RegExp Match A
2) Column 2 (TRUE) Scorecard
- Add a Scorecard;
- Drag and Drop the field Column 2 onto the Metric field and change the aggregation to COUNT;
- Create and apply the Filter: Include Column 2 RegExp Match TRUE
3) Ratio Metric
- Select both Scorecards: Click on the Column 1 (A) Scorecard and then Ctrl + Click on the Column 2 (TRUE) Scorecard Scorecard;
- Blend Data: Right click on one of the selected Scorecards and select Blend data from the Drop-down.
Google Data Studio Report to demonstrate, as well as a GIF showing the process:
Approach 2: CASE Statements
An approach with CASE statements (create formula #1 and #2 at the Data Source-level; formula 3 can be created at the Data Source-level or Chart-level if required):
1) Column 1 (A)
CASE
WHEN REGEXP_MATCH(Column 1, "A") THEN "A"
ELSE NULL
END
2) Column 2 (TRUE)
CASE
WHEN REGEXP_MATCH(Column 2, "TRUE") THEN "TRUE"
ELSE NULL
END
3) Column 1 (A) / Column 2 (TRUE)
COUNT(Column 1 (A)) / COUNT(Column 2 (TRUE))
Added a New Page to the Google Data Studio Report to demonstrate as well as a GIF showing the process above: