I solved one issue: x1*y2 using expression **(location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x)) Apply when idm:position($this/parent()) = 1 expression (location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x)) Apply when idm:position($this/parent()) !=1**. probably my apply when condition is not ok, I am not sure. I checked in excel everything is right. Now my problem is that I want same calculation as above but that would be with last and first position of the coordinate. How can I perform that work?work?

I solved one issue: x1*y2 using expression **(location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x)) Apply when idm:position($this/parent()) = 1 expression (location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x)) Apply when idm:position($this/parent()) !=1**. I checked in excel everything is right. Now my problem is that I want some same calculation as above calculation but that would be with last and first. first position of the coordinate. How can I perform that work?

I solved one issue: x1*y2 using expression **(location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x)) Apply when when idm:position($this/parent()) = 1 expression (location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x)) Apply when idm:position($this/parent()) !=1**. I checked in excel everything is right. Now my problem is that I want some calculation as above calculation but that would be with last and first. How can I perform that work?

I solved one issue: x1*y2 using expression **(location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x)) Apply when idm:position($this/parent()) = 1 expression (location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x)) Apply when idm:position($this/parent()) !=1**. I checked in excel everything is right. Now my problem is that I want some calculation as above calculation but that would be with last and first. How can I perform that work?