Calculation errors

[Alistair]

I am running into calculation errors that seem to be coming from Revolution.

I am reading the settings of three scrollbars using statements of the form:

put the thumbposition of scrollbar "Efield" into Efield

When I display Efield the value is correct. If I move one or more of the scrollbars and then bring them back to their original positions, the values of the variables are always correct but the result of the calculation changes. How can this occur.

Also, if a set a scrollbar to range from 0 to 100 I find that it is not possible to set the scrollbar to either 50 or 150.

[Mark]

post your script

[Alistair]

Here is the part of the script where the problem is occurring

I am using the second PUT statement to watch the values of the variables and the result of part of the calculation



put the thumbposition of scrollbar "mIz" into mIz
put the thumbposition of scrollbar "Efield" into Efield
put the thumbposition of scrollbar "Bfield" into Bfield
if bfield <> 0 then
put scaleFac*sqrt(2*mIz*Efield/(Bfield*Bfield)) into r1
put mIz, Efield, Bfield, 2*mIz*Efield/(Bfield*Bfield)
end if

[Mark]

Hi Alistair,

I guess that the value of scaleFac changes. Is it posible that the startValue and endValue of the scrollbars change?

Best,

Mark

[Alistair]

Hi Mark

No the startValues and endValues and the scalefactor don't change. When I display the values of the variables they are correct. It seems to be the calculation itself that is producing a varying result.

[Mark]

Hi Alistair,

What are the values and what are the results?

Mark

[Alistair]

Hi Mark

As an example, if Miz is set to 100 and EField is set to 1, then repeatedly setting Bfield to 2 (setting the slider to another value, then setting it to 2) produces the following results: 2.636, 2.670, 2.705, 2.740. The correct value is 2.72.

[Klaus]

Hi Alistair,

I also experienced some strangeness with scrollbars in the past, they were returning fractions althougg I did not set the numberformat of anything else.

The range was from -4 to 4.

So I ended with somthing like:

Code: Select all

...
put ROUND(the thumbpos of sb "whatever scrollbar") into sb_value
...

And my calculations were correct and happy ever after

Hope that helps.


Best from germany

Klaus

[Alistair]

Hi Klaus

Adding Round did solve the problem for integer values but the problem is that the range is meant to go from 0 and therefore fractional values such as 0.3 and intermediate values,say, between 1 and 2 are valid.

[Klaus]

Hi Alistair,

you can define the number of fractions that ROUND should return with a second parameter to that function, see the docs for ROUND:

put round(100/3,1) -> 33.3
put round(100/3,2) -> 33.33
etc...


Best

Klaus

[Alistair]

Hi Klaus,

Thanks for that suggestion. That fixed the problem. I should have thought to check the Dictionary when you first suggested using the Round function.

Thanks again

Alistair

[Mark]

Hi Alistair,

One more idea: add the following brief script to your slider object and make sure to set the showValue of the slider to false or set the pageInc to 0, to hide the tics (you'll need to experiment with what works best for you).

Code: Select all

on mouseUp
   set the thumbPos of me to round(the thumbPos of me)
end mouseUp

If you use this script while the tics of the slider are visible, you will see that the tics are purely cosmetic and also confusing.

Best,

Mark

[Alistair]

Hi Mark

Thanks for that suggestion. I am using the slider to set a value so in this case displaying the value is important.

Regards

Alistair

[Mark]

Alistair, just to make sure that I'm clear, you can display the value without displaying the tics.

Mark

[Alistair]

Yes, thanks, Mark. I'm displaying the value but not the tics.

Alistair