topic Re: Qlik's issue with basic calculations in App Development

Qlik's issue with basic calculations

Anonymous — Tue, 24 Oct 2017 12:02:49 GMT

Hi,

I use the September 2017 version.

I found an (funny?) issue with basic calculations in Qlik Sense.

Let's assume:

a=1

b=1+3

result = $(a)/$(b)

Now it's time for the question - result is equal.....

Should be 0,25, right? (1 divided by 4)

Not for QlikSense! For QlikSense the results equals 4.

I started investigation how it's possible.

It seems that Qlik instead of this:

a) calculate a variable

b) calculate b variable

c) divide: a/b

Does this:

a) do not calculate a and b

b) copy raw formulas (from variables) to the result: result = 1 / 1 +3

c) calculate it right now..

So the result is 1/1 +3 = 1+3=4

Instead of 1/4...

Is this a known issue?

Are you (Qlik team) going to solve this problem? Maybe in the November 2017 version?

Re: Qlik's issue with basic calculations

stigchel — Tue, 24 Oct 2017 12:32:39 GMT

This is as intended, should you want the outcome to be 0.25 then use $(=a)/$(=b)

The Little Equals Sign

Re: Qlik's issue with basic calculations

mdmukramali — Tue, 24 Oct 2017 12:38:02 GMT

Hi,

The Order of Operations:

"Parentheses, Exponents, Multiplication and Division, and Addition and Subtraction"

The Expression should be like = $(a)/($(b))

because you saved a and b values are in a string.

a 1

b 1+3

the calculation will be

=1/1+3

first, it will divide 1/1 then it will do addition 3.

While creating variable b you can use = symbol it will calculate the value ( =1+3 ) (4)

Re: Qlik's issue with basic calculations

Anonymous — Tue, 24 Oct 2017 13:20:10 GMT

Nope.

It's still 4.

The Little Equals Sign doesn't work here.

Re: Qlik's issue with basic calculations

Anonymous — Tue, 24 Oct 2017 14:13:14 GMT

1. It's not about the order of operations.

It's about the process of calculation in Qlik Sense.

2. If you have

x=2+3

and you have to multiply 2*x

what will you do?

2*(2+3) or 2*2+3

Of course the first answer is correct.

That's the logic of using variables/unknowns

The problem is that Qlik is using the second (wrong) way.

3.Using the equals sign in the definition of b variable is not a good choice.

Maybe in this example it doesn't change too much.

But - if the definition of "b" variable is more complex, the equals sign may have impact on the results of the "b" value.

4. Of course, I can put everything into brackets, but I am not looking for "workaround".

This should works correctly as in other softwares, scripting/programming languages etc.

Re: Qlik's issue with basic calculations

stigchel — Tue, 24 Oct 2017 14:38:11 GMT

My bad

Either change the variable definition to include the = sign

=1+3

instead of

1+3

or use

$(=$(b))

In your expression

Re: Qlik's issue with basic calculations

Anonymous — Wed, 25 Oct 2017 07:51:04 GMT

Thanks - Finally, $(=$(b)) is working

So, instead of 3 characters a/b, I have to use 17 characters: $(=$(a))/$(=$(b))

Good that the syntax is so clear We need to add ONLY 8 x brackets, 4 x dollar signs and 2 x equals signs

Nice improvement Qlik

This is an example of incosistency.

$(a) returns 1, $(b) returns 4, $(a)/$(b) is wrong and returns 4

So you have to use $(=$(b)).

But $(=$(b)) doesn't work while you have definition with any field like b=[Field]+3

...

no comments

To be honest - this is the simplest example of using two variables.

If I have to use 17 characters to divide two variables (with 8 brackets!) what would happen if have to use 5 variables?

Please take a look at this simple calculation:

$(=$(a))/$(=$(b))*($(=$(b1))*$(=$(b2))-$(=$(c)))

Fortunately, Qlik helps us with syntax highlighting

Nope!

it doesn't help of course, there is still no good syntax highlighting

If this is intended... God help us

Re: Qlik's issue with basic calculations

jonvitale — Thu, 02 Nov 2017 12:56:28 GMT

I disagree that this is wrong.

When you do a dollar sign expansion you are substituting text exactly as it is written. So if I have

a = 2+3

b = 2 * $(a)

I SHOULD get 2 * 2 + 3 according to the rules of dollar sign expansion. This may not be what I intended (I might want 10 as my answer, and this will give me 7), but it is the consistent way that dollar sign expansions work. If you want 2+3 to be treated as a group, then use parentheses (2+3).

Re: Qlik's issue with basic calculations

Nacho — Thu, 02 Nov 2017 16:03:08 GMT

I think it is correct.

1/1 + 3 = 1 + 3 = 4

Re: Qlik's issue with basic calculations

Anonymous — Fri, 03 Nov 2017 10:18:59 GMT

I understand the operation of $() expansion.

I said it wrong beacause it's illogical and unintuitive.

If you define:

a=1

b=1+3

The results of a/b will be:

in C# 0,25

in VBA 0,25

in JS 0,25

in Maths 0,25

and so on..

in Qlik it's 4, cause it doesn't calculate varaibles before using.

The way of using variables in Qlik is opposite to standards and logic.

And finnally it's ridiculous because to write correctly this simple expression:

a/(b+c/d)

you have to use 37 characters

$(=$(a))/($(=$(b))+$(=$(c))/$(=$(d)))

and the expression is unreadable

Re: Qlik's issue with basic calculations

Lucke_Hallbergson — Fri, 03 Nov 2017 11:58:21 GMT

Look at "let" vs "set" in help.

Let: Calculates the expression assigned to it and sets the expression result to the variable.

Set: Assigns the value(or expression which is after the equal sign) as it is without compute.

https://help.qlik.com/en-US/sense/June2017/Subsystems/Hub/Content/Scripting/ScriptRegularStatements/Set.htm

https://help.qlik.com/en-US/sense/June2017/Subsystems/Hub/Content/Scripting/ScriptRegularStatements/Let.htm

Regards

Lucke

Re: Qlik's issue with basic calculations

Anonymous — Fri, 03 Nov 2017 13:12:18 GMT

It not related to "let" or "set" keyword. It's not about "data load variables".

Please read the post before answer.

Re: Qlik's issue with basic calculations

jonvitale — Fri, 03 Nov 2017 13:19:38 GMT

I see what you're saying, I get it, but I I think that it does follow the logic of dollar sign expansion - which does not do any computation - it just replaces variables in a literal manner.

By the way, one thing that has been overlooked in this discussion is "set" vs. "let":

If you do the following

let a = 1;

let b = 1+3;

let c = a/(a+b);

You will get the expected value for 'c', 0.20.

Try it.

Re: Qlik's issue with basic calculations

Anonymous — Fri, 03 Nov 2017 13:55:09 GMT

I see, but it's not related to data load editor. So the "let" and "set" keywords don't resolve the problem.

It's a little tricky and unintuitive.

Who wants to use variables as replacements of text formulas?

If you use e.g.

margin=0.1*Price-Discount

you want to keep results of the expression, not expression itself.

Who is interested in keeping text string "0.1 * Price - Discout" instead of exact number?

For me - more usefull (if we are talking about variables) is result, not the text of formula.

So the $(var) should return value, and more complex syntax like $(=$(var)) should return "text formula".

Re: Qlik's issue with basic calculations

rwunderlich — Wed, 22 Nov 2017 16:48:21 GMT

I think you are mixing up a number of concepts and rules.

As a best practice, you should always enclose variables that contain operators in parens to avoid order of operation issues. So recommended would be:

a: 1

b: (1+3)

and then "$(a) / $(b)" would return the correct result.

You made the assertion:

----------------------------

if you define:

a=1

b=1+3

The results of a/b will be:

in C# 0,25

in VBA 0,25

JS 0,25

-------------------------------

That would be true if a and b were created using numeric expressions as you show in the example. You can do the same thing in Qlik Sense load script;

a = 1;

b = 1+3;

Then the expression "a / b" would equal 0.25, as you are expecting.

However, when you enter variable values using the variable editor, the values are always strings. So if we return to the C#/JS example, the statements would be:

a="1";

b="1+3";

a/b would not return a correct result.

If you want to enter 1+3 in the variable editor, and you want it to be stored as the result of that expression, you can preceed the expression with an = sign, which will cause the result "4" to become the value of the variable. This is just as it is in your C#/JS example, you have to use an = if you want 1+3 to be treated as 4.

-Rob

Re: Qlik's issue with basic calculations

rwunderlich — Wed, 22 Nov 2017 16:55:13 GMT

Who wants to use variables as replacements of text formulas?

If you use e.g.

margin=0.1*Price-Discount

you want to keep results of the expression, not expression itself.

Using variables is probably 90% of the use of variables in Qlik. The reason we want the text, not the result, is that evaluation must be deferred to the chart row where it will be calculated using the data for that row.

Using your example above, we want the Price and Discount for the current row when we make the calculation.

-Rob