I think there is a misunderstanding about the reason for this attribute.

The attribute means that the result of the equation is given back as a logical number, if possible.

So if your equation result is a string '52' and you want to use it in a followup-equation the attribute enforces it as 52 (numeric). So in your followup-equation you can just write {q1+12}

OK,

Then if you do :
EQ2 : {EQ2} : you must have '' (or NaN according to doc) in any condition ?

But broken here (see attached survey)

• OK i same group
• Different in another group

PS: documentation:
<quote>Equation: Setting this option to "Yes" will force equation results to be converted to a numeric value. If the equation result is not a number (and not blank), the equation will return NaN. </quote>
http://manual.limesurvey.org/Question_type_-_Equation#Numbers_only_.28numbers_only.29

Denis, can you take this one, then? The documentation should be right.

Yes sure

Fix committed to 2.06 branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=14236

LimeSurvey 2.05+ Build 140618 released.