org-table, empty cells and nan

[Uwe Brauer <oub@mat.ucm.es>]

Hi 

I have the following table(s)



| Name  | Exam1 | Exam2 | Exercises | Ex1_Ex2 | Total |
|-------+-------+-------+-----------+---------+-------|
| Smith |       |  7.90 |           |    5.81 | NP    |
#+TBLFM: $6=if("$2" == "nan", string("NP"), 0.65*$2+0.25*$3+$4); E f-1

However when colum 2 is not empty but colum 4 is then I obatin *nan*

| Name  | Exam1 | Exam2 | Exercises | Ex1_Ex2 | Total |
|-------+-------+-------+-----------+---------+-------|
| Smith |   5.9 |  7.90 |           |    5.81 |   nan |
#+TBLFM: $6=if("$2" == "nan", string("NP"), 0.65*$2+0.25*$3+$4); E f-1


A solution is to put 0 in colum 4, but for some reasons which are a
complicated to explain, I want to avoid that.

| Name  | Exam1 | Exam2 | Exercises | Ex1_Ex2 | Total |
|-------+-------+-------+-----------+---------+-------|
| Smith |   5.9 |  7.90 |         0 |    5.81 |   5.8 |
#+TBLFM: $6=if("$2" == "nan", string("NP"), 0.65*$2+0.25*$3+$4); E f-1



Any idea how to deal with the situation?

Regards

Uwe Brauer