topic Re: Use previous row as current row calculation in Talend Studio

Use previous row as current row calculation

Anonymous — Thu, 21 Jan 2016 14:52:08 GMT

hi all,
i just wonder how talend can get previous row value to be used in current row mathematical calculation. Example:

A X1 Y1 = (Y0-X1)*A
----------------------------------------
-- -- 0
1 5 (0 - 5)*1 = -5
2 3 (-5-3)*2 = -16
3 6 (-16-6)*3 = -66
4 2 (-66-2)*4 = -272

How do i can calculate formula Y1 as above.

i really appreciate your help.

Thanks.

Re: Use previous row as current row calculation

Anonymous — Sun, 24 Jan 2016 02:55:48 GMT

Hi all,
Plz help me

Re: Use previous row as current row calculation

Anonymous — Sun, 24 Jan 2016 03:57:41 GMT

Hi
You can store the calculation result to a global variable on tJavaRow for used later. eg:
...tMap--main--tJavaRow

Doing the calculation on tMap:
(Integer)globalMap.get("result")==null?(0-row1.X1)*row1.A: ((Integer)globalMap.get("result")--row1.X1)*row1.A

on tJavaRow:
globalMap.put("result", input_row.Y1);

Re: Use previous row as current row calculation

Anonymous — Thu, 25 Feb 2016 04:41:50 GMT

Hi shong,

I have tried the solution above, but its still not working.
My condition is (Double)globalMap.get("result") == null ? 100.0 : (Double)globalMap.get("result") + 1
But the result return as picture below.

Re: Use previous row as current row calculation

Anonymous — Thu, 25 Feb 2016 06:21:34 GMT

I see you use another expression to calculate the data, what's your input data? What are your expected result?

Re: Use previous row as current row calculation

Anonymous — Thu, 25 Feb 2016 07:09:38 GMT

I can see an example here .Let us know if it helps :

https://talendtutorials.wordpress.com/

Re: Use previous row as current row calculation

Anonymous — Thu, 25 Feb 2016 08:40:58 GMT

Example:

Ty Survival_Ft
--- -------------
0 100
1 100 + 1 = 101
2 101 + 1 = 102
3 102 + 1 = 103
4 103 + 1 = 104

I want to use the previous row answer to calculate for the next row.
Thanks.

Re: Use previous row as current row calculation

Anonymous — Thu, 25 Feb 2016 08:57:59 GMT

Take a look at tMemorizeRows component, this component can fit your need.