calculate correlation using variable

[curiousfellow]

I want to calculate the correlation between the answers of two questions.

So I made a variable to calculate the sum of one question. (OverallQuestion) :=Sum({1<question={'finalquestion'}>}answer)

The answer to the questions is allways numeric (or null)

However when I make an expression like  =correl($(Overallquestio),Question) i don't get results.

Some questions were not answered, so there are null-values

Is it possible to use variables in the function Correl ?

[marcus_sommer]

Generally you could use variables for nearly each part from dimensions or expression - it's only a question from the syntax.

If you used the syntax "= AnyExpression" for a variable the variable will be global calculated without any relation to objects or dimensions. If you want use the variable as replace for a expression then without the equal-sign. Further the call from variables needed often a $-expansion like $(=variable), see also:

The Magic of Variables

The Magic of Dollar Expansions

Therefore try something like this:

variable:

Sum({1<question={'finalquestion'}>}answer)

expression:

correl($(=Overallquestion),Question)

And by problems with NULL could be a rangecorrel() helpful.

- Marcus

[curiousfellow]

For $(=Overallquestion) I get a result. But when I enter Correl($(=Overallquestion),$(=Overallquestion)) I don't get a result (only a '-'). Should be 1

Strange.. or am I missing something ?

[marcus_sommer]

Maybe there are any invalid values or NULL on the level from the aggregation. Try to handle it with rangecorrel() or $(=alt(Overallquestion, DefaultValue)).

- Marcus

[gshockxcc]

Your variable "OverallQuestion" contains a basic aggregation function.  You can't use this in Correl unless you use TOTAL.

See if this fixes your error.