Previous Read Row

[marcel_olmo]

Hi guys, I've the following example :

Field1	Field2	Result
1	10	1
2	20	2
3	30	3,5
4	40	5,5
5	50	8

Where the field Result needs the value of the previous value of Result itself.

I know that you can get the previous value of Field1 or Field2 because there aren't the same column fields, but when is the same column, it says "error" because Qlik can't find the field "Result" because it doesn't even exist.

Here's the calculation I can't do in Qlik --> Result =(previous(Result)*2 + Field1 )/2

How can you do that?

I attack an excel example of what I mean.

Regards, Marcel.

[maxgro]

LOAD Field1,

     Field2,

     alt((previous(Result)*2 + Field1 )/2, Field1) as Result

FROM

[Prev Row Example.xlsx]

(ooxml, embedded labels, table is Hoja1);

[swuehl]

PEEK() can do what you want, addressing the output from the row loaded before:

LOAD Field1,

          Field2,

          Rangesum(Peek(Result)*2, Field1 )/2 AS Result

FROM ....;

edit: Corrected rangesum() arguments separated by comma

[marcel_olmo]

Thanks Massimo for answering so quickly,

the point is that there's no Result column in my database, I have to calculate it from Field1 and Field2. This is an example trying to show what I'm trying to do.

My result field is something like :

if( rowno() =1,1, (previous(NewField) * 2 + Field1)/2 as NewField.

If you do that, Qlik says that "NewField" it doesn't exists.

How can you do that?

Regards, Marcel.

[marcel_olmo]

Thanks swuehl,

I've just wrote the point of that in the answer before. There's no such Result field in the database, that's why Qlik doesn't let me do that.

I've attached what I mean.

Regards, Marcel.

[swuehl · Accepted solution]

Have you even tried the script I've posted?

I am not loading the Result column, but calculating it from Field1 and the previous output table row only.

I do get Result 0.5 off, but that's what your expression returns.

edit: emphasized that peek() returns previous output table row and uploaded sample QVW

[antoniotiman]

Hi Marcel,

simply You add

If(RowNo() > 1,Swuel' expression,1) as Result

Regards

[marcel_olmo]

Thanks swuehl,

I've got the issue there. If you use the function Previous() it says the field doesn't exist, but not the function peek().

Thanks a lot for your useful help.

Regards, Marcel.

[maxgro]

LOAD Field1,

     Field2,

     alt((peek(Result2)*2 + Field1 )/2, Field1) as Result2

FROM

[Prev Row Example.xlsx]

(ooxml, embedded labels, table is Hoja1);