Pivot Tables
 

Hello. Is there a way for pivot tables to count a field only if it contains a
string of characters?
Example data:

number results
1 a,b,c
2 a,b,c
3 a,b,c
4 b,c,d
5 b,c,d
6 a,b
7 e,f
8 a,b,c
9 a,b,c
10 a,b,c
11 b,c,d
12 b,c,d
13 a,b
14 e,f
15 a,b,c
16 a,b,c
17 a,b,c
18 b,c,d
19 b,c,d
20 a,b
21 e,f

I want to count results that contain "a", and results that contain "b" etc.

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Thanks,
Mike