I am totaling the questions by section and it is giving me NaN.

The previous are now working fine leaving blanks where the question is not answered. Now, totaling the different questions is giving me NaN. All the questions have to be answered (AND CORRECT) then NaN clears and it offers the correct total!.

In the ODK Form Logic, unanswered number questions are nil. That is, they have no value. When a variable referencing an empty value is used in a math operator or function, it is treated as Not a Number (NaN). The empty value will not be converted to zero. The result of a calculation including NaN will also be NaN, which may not be the behavior you want or expect.

To convert empty values to zero, you can use either the coalesce() function or the if() function.

I am familiar with the NaN issue and the fact it is normally cleared by the coalesce function.
In my case it has not worked with previous options. Hence the workaround that @Kal_Lam advised that solved my headache, by using the relevant column.

I now have to total the earlier calculated variables and they are not working. Even after using your suggestions, copy-pasting them in case it was error on my part.

I’ve attached the XLS form that has the info to make sense of.

@amailuk, I would use it as coalesce(${c1}, 0) + coalesce(${sum2}, 0) + coalesce(${c3}, 0) + coalesce(${sum4}, 0) + coalesce(${c5}, 0) instead of using it this way coalesce(${c1}+${sum2}+${c3}+${sum4} +${c5}, 0).