topic Re: Field generation within while loop in QlikView

Field generation within while loop

AmCh — Wed, 10 Mar 2021 11:41:58 GMT

Hello everyone,

In a while loop I am supposed to calculate a value in each iteration.

As an example:

set b=2;

set a=0;

set n=100;

set delta=(b-a)/n;

do while t<b

let W=W+$(t)*$(t);

let t=t+delta;

Loop

For post-processing, I would like to store these values in a field to be able to display them later in a diagram. For the chart I would need dimension and expression.

Dimension=values of t

Expression=values of W

Can someone please help me?

Thank you very much in advance.

With kind regards

Re: Field generation within while loop

edwin — Wed, 10 Mar 2021 17:52:28 GMT

assuming the loop is already working and that the t , delta, and w already exists as variables:

noconcatenate TABLE: load null() as t autogenerate(0); do while t<b let W=$(W)+$(t)*$(t); let t=$(t)+$(delta); concatenate(TABLE) load $(t) as t, $(W) as W autogenerate(1); Loop

when you use the variable i think you need to encapsulate it with $(). but you need to test it

Re: Field generation within while loop

edwin — Wed, 10 Mar 2021 17:53:10 GMT

this look the same as a different post

Re: Field generation within while loop

AmCh — Wed, 10 Mar 2021 20:12:41 GMT

Thank you for your prompt response.

What do you mean with that t, delta and w already exist as variable?

t is an increment variable within the loop. It should not be pre-defined.

delta is already pre-defined as : set delta=(b-a)/n.

w should be created within the loop. It should not be pre-defined.

Another problem here that I couldn't increment with a non decimal value. (e.g. delta=0.5)

Re: Field generation within while loop

edwin — Wed, 10 Mar 2021 20:21:45 GMT

if your increment is by .5 from 0 to 4 for example, you can loop from 0 to 8 and just divide your counter by 2 to simulate a .5 increment

Re: Field generation within while loop

AmCh — Wed, 10 Mar 2021 20:29:27 GMT

Thank you. It worked with the increment. But it didn't with the main problem; storing of variables within the while loop.
Can you help me further.
Thank you in advance.

Re: Field generation within while loop

edwin — Wed, 10 Mar 2021 21:49:55 GMT

when you say it didnt work, what didnt work? was there an error message? can you give a hint?

Re: Field generation within while loop

edwin — Thu, 11 Mar 2021 13:08:34 GMT

try this:

set b=2;
set a=0;
set n=100;
set delta=(b-a)/n;

let W=0;
let t=0;

data:
load null() as t AutoGenerate(0);

do while t<b
let W=W+t*t;
let t=t+$(delta);
concatenate (data) load $(t) as t, $(W) as W AutoGenerate(1);
Loop

Re: Field generation within while loop

AmCh — Mon, 29 Mar 2021 15:44:25 GMT

Hi edwin,

thank you for your reply. Unfortunately this error messages appears:

'Field names must be unique within table'

Only two fields should be generated (t and W)
I want to generate rows in respective fields.

Any help please?
Thanks in advance.

Re: Field generation within while loop

edwin — Fri, 09 Apr 2021 20:18:26 GMT

@AmCh i ran the script and there weren't any errors. this means you modified it and i get that. if you still need help maybe you can share your script?