NAN?

[Labtrainer]

Hi,

I am using the chassis for compact DAQ with NI 9211 24 bit thermocouple differential analog input module. I have made a program in labView to determine mass flow etc…

However, once the mass flow has reached a value close to zero during a test, the indicator shows NAN. Is there a way to change that to a value of 0?

Thank a lot

Regards-Glenn

[tst]

NaN means Not a Number and is a special value defined for an invalid number (like what you get if you divide by 0), so your number should not be "close to 0" but an invalid number.

If you still want to display 0 instead of NaN, you can use the Not a Number\Path\Refnum function from the comparison palette which will return T if the number is NaN and replace the value, but I would not recommend that in most cases.

[johnsold]

Glenn,

NaN (Not a Number) occurs when some mathematical operations such as divide by zero occur.

Best is to test the data before it enters an operation which could result in NaN. If you cannot do that, use the Not A Number? function from the comparisons palette to detect the NaNs and replace them with 0 or what ever is appropriate.

Lynn

[altenbach]

Yes. The comparison palette has a test for "Not a number/path/refnum". Use a select as in the image below.

Of course it could be that the NaN points to some fundamental problem that should be adressed earlier. Do you know why you are getting NaNs? 😉

Message Edited by altenbach on 03-12-2007 10:24 AM

[altenbach]

Either I have to type really fast or refrain from making images to avoing being in third place all the time. 😄

[Ben]

"

Either I have to type really fast or refrain from making images to avoing being in third place all the time.

"

Well you still manage to beat me to the punch even with images!

Ben

[johnsold]

The rest of us just want to make sure the best is saved for last.

Lynn

[Labtrainer]

Thanks guys.

That s really helpful

Glenn

[Kevin_Price]

A little off-topic, but here's one little NaN tidbit:

I've found them useful as default values on wired controls in (semi-)intelligent subvi's.  This gives me a means for determining whether the caller function wired an input or not.  After checking for NaN, I can then decide whatever I want to use as a replacement value, and that decision can be dynamic. 

For example, I may store the most recent "legal" input in an unitialized shift register, which I can then use in place of an unwired "NaN" input.  Or I may make a vi for PV=nRT which can auto-detect which inputs are wired and know how to calculate the other parameter.  Etc.

Share and enjoy...

-Kevin P. 

[altenbach]

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@Labtrainer wrote:

Thanks guys.

That s really helpful

---

Glenn,

You're welcome! One easy way to thank would be to just look in the lower right corner of each reply and click on the circle that's all the way to the right. 😄

Christian