Conditional Distinct Count in Crystal Reports - crystal-reports

Question

I have a dataset like this:
ID PersonID ClassID Attended Converted
1 1 1 1 0
2 1 1 1 1
3 1 1 1 1
4 2 1 1 1
5 3 2 0 0
6 3 2 1 1
7 4 2 1 0
I'm building a report that groups by ClassID (actually I'm using a parameter that allows grouping on a few different cols, but for simplicity here, I'm just using ClassID). I need to do a calculation in each group footer. In order to do the calculation, I need to count records with PersonIDs unique to that group. The catch is, in one case, these records also need to match a criteria. EG:
X = [Count of records where Converted = 1 with distinct PersonID]
Y = [Count of records where Attended = 1]
Then I need to display the quotient as a percentage:
(X/Y)*100
So the final report would look something like this:
ID PersonID Attended Converted
CLASS 1 GROUP
1 1 1 0
2 1 1 1
3 1 1 1
4 2 1 1
Percent= 2/4 = 50%
CLASS 2 GROUP
5 3 0 0
6 3 1 1
7 4 1 0
Percent= 1/2 = 50%
Notice in Class 1 Group, there are 3 records with Converted = 1 but 'X' (the numerator) is equal to 2 because of the duplicate PersonID. How can I calculate this in Crystal Reports?

Answer 1

I had to create a few different formulas to make this work with the help of this site.
First I created a function called fNull as suggested by that site, that is just blank. I was wondering if just typing null in its place would do the job but didn't get to testing it. Next I created formulas to evaluate if a row was attended and if a row was converted.
fTrialAttended:
//Allows row to be counted if AttendedTrial is true
if {ConversionData.AttendedTrial} = true
then CStr({ConversionData.PersonID})
else {#fNull}
fTrialsConverted:
//Allows row to be counted if Converted is true
if {ConversionData.Converted} = true
then CStr({ConversionData.PersonID})
else {#fNull}
Note that I'm returning the PersonID if attended or converted is true. This lets me do the distinct count in the next formula (X from the original question):
fX:
DistinctCount({#fTrialsConverted}, {ConversionData.ClassID})
This is placed in the group footer. Again remember #fTrialsConverted is returning the PersonID of trials converted (or fNull, which won't be counted). One thing I don't understand is why I had to explicitly include the group by field (ClassID) if it's in the group footer, but I did or it would count the total across all groups. Next, Y was just a straight up count.
fY:
//Counts the number of trials attended in the group
Count({#fTrialsAttended}, {ConversionData.ClassID})
And finally a formula to calculate the percentage:
if {#fY} = 0 then 0
else ({#fX}/{#fY})*100
The last thing I'll share is I wanted to also calculate the total across all groups in the report footer. Counting total Y was easy, it's the same as the fY formula except you leave out the group by parameter. Counting total X was trickier because I need the sum of the X from each group and Crystal can't sum another sum. So I updated my X formula to also keep a running total in a global variable:
fX:
//Counts the number of converted trials in the group, distinct to a personID
whileprintingrecords;
Local NumberVar numConverted := DistinctCount({#fTrialsConverted}, {#fGroupBy});
global NumberVar rtConverted := rtConverted + numConverted; //Add to global running total
numConverted; //Return this value
Now I can use rtConverted in the footer for the calculation. This lead to just one other bewildering thing that took me a couple hours to figure out. rtConverted was not being treated as a global variable until I explicitly added the global keyword, despite all the documentation I've seen saying global is the default. Once I figured that out, it all worked great.