topic Re: Parse a mathematical formula in QlikView

Parse a mathematical formula

GuillaumeRUE — Wed, 25 Nov 2020 16:16:04 GMT

Hello,

I would like to know if it's possible to parse a string of a mathematical formula and get the result?
For example, I get from my DB something like '98+2' as a string, and I would like to print the result.

Then if it's possible, can I change a variable in the formula?
For example, if I have '(value+5)*8' , can I change value by something else, a real variable?

Thank's in advance

Guillaume

Re: Parse a mathematical formula

marcus_sommer — Thu, 21 Feb 2019 12:51:00 GMT

Try it with something like: evaluate(string) as Result

- Marcus

Re: Parse a mathematical formula

GuillaumeRUE — Thu, 21 Feb 2019 13:56:43 GMT

This perfect for simple expressions like '50+2'.

Do you know if I can now manage to parse expressions like 'value+2'?
My goal is to change value (which is a string) by a variable.

Re: Parse a mathematical formula

marcus_sommer — Thu, 21 Feb 2019 14:10:35 GMT

Maybe you could a parametrized variable for it, something like:

set exEvaluate = "evaluate($1 + 2)"; /* just $1 + 2 might be also working, it's depending on your value */

and then a call like:

$(exEvaluate(value))

- Marcus

Re: Parse a mathematical formula

GuillaumeRUE — Thu, 21 Feb 2019 14:21:02 GMT

I can try this solution.

But the problem that I see is my expression is not always 'value+2',

it can be somethng like '(value/8)*0.5'

or '0.5*((value+4)/0.2)+89'

So I imagine the best solution should be to find the part of my string where there is the word 'value' and change it by my variable, if it's possible.

Re: Parse a mathematical formula

marcus_sommer — Thu, 21 Feb 2019 14:49:55 GMT

With the above mentioned approach you could use as many parameters like you want and you could also extract/strip some content from a parameter - nearly everything will be possible if you could apply a stable logic, for example:

set exEvaluate = "evaluate($1 $2 $3 $4 $5 $6 $7 $8 $9)";

$(exEvaluate(0.5, *, value, +, 4, /, 0.2, +, 89))

and I think there are also ways to define a certain calculation-order probably the easiest approach is just using severals of such customized-functions but thinkable are also other ways which contain the brackets.

- Marcus

Re: Parse a mathematical formula

GuillaumeRUE — Thu, 21 Feb 2019 15:21:32 GMT

Ok Thank you, I will try this solution.

I'll keep you informed!