Replace null value with expression output

[#1]

My Scenario is

Group      Amount

  A             100

  B             200

  C             

   D              400

   E            

convert to

Group   Amount

A           100

B             200

C             300 i.e (B+A)

D              400

E                500  i.e (D+A) 

there can be more null values like E and C .

New sum (Amount ) is calculated after replacing null with values.

[alexandros17]

Try something like:

If(isnull(myField), Sum(previous(myField), myField)

[maxgro]

SCRIPT

Source:

load * inline [

Group,    Amount      

A,        100

B,        200

C,         

D,        400

E,           

];

Final:

NoConcatenate load

Group,

// when Amount is null sum previuos Amount and Amount of first row (A)

if(len(trim(Amount))=0, peek(Amount) + peek(Amount, 0), Amount) as Amount

Resident Source

order by Group;

drop Table Source;

RESULT

Group	Amount
A	100
B	200
C	300
D	400
E	500

[#4]

Thanks For Reply.

But One more concern is that we are taking value by specifying index to peek() but I want the value to peek

by matching the group and logic to fill different null values are different.

Can i achieve this in front end using IF or may be by Set Analysis.

[maxgro]

if  the logic is different for every Group with missing Amount  you may try in a chart ordered by Group with

DIMENSION Group

EXPRESSION

if(Group='C', concat(total aggr(if(Group='A', sum(Amount)), Group), '-', Group) + above(sum(Amount)),

if(Group='E', concat(total aggr(if(Group='A', sum(Amount)), Group), '-', Group) + above(sum(Amount)),

sum(Amount) ))