topic Re: areaundercurve in LabVIEW

areaundercurve

weeke — Sat, 28 May 2011 14:39:00 GMT

how to calculate area under curve.

i want to calculate area under the positive and negative cycles of green plot.

thanks

Attached VI

Re: areaundercurve

altenbach — Sat, 28 May 2011 15:30:03 GMT

The green plot is never negative, so what exactly do you mean by a negative cycle of the green plot?

Re: areaundercurve

weeke — Sat, 28 May 2011 15:55:05 GMT

Sorry for not mentioning that

I meant to say when you change the white slider, the green plot will go above the Red. That would be the positive cycle.

This is what i meant my negative cycle which in this situation means the area when green is below the Red.

please change the slider position up and down to observe the situation

Re: areaundercurve

altenbach — Sat, 28 May 2011 16:02:27 GMT

So you want to count the area below the red as negative or not?

(I.e. do you want to add the areas above and below 0.5 or do you want to subtract the area below 0.5 from the area above 0.5?)

Re: areaundercurve

weeke — Sat, 28 May 2011 16:27:21 GMT

I want to measure area above and below 0.5 both, and store both values in a table.

And yes i want to subtract the area above with the area below and store the value in the table.

Re: areaundercurve

altenbach — Sat, 28 May 2011 16:30:42 GMT

Here is a quick draft showing both options.

Subtract the green from the red, then simply multiply each new point with dt (0.1s in this case) and add to a shift register or feedback node. Take the absolute value if desired.

Please veryfy correct operation and modify as needed.

What do you mean by "store in a table"? Do you heed help with that or are you OK with this?

Re: areaundercurve

weeke — Sat, 28 May 2011 16:55:44 GMT

yes i need help with building a table

What i have observed is that when green is above Red, it would start incrementing in the signed integral value and when it is below red it would start decrement in the current value.

What i want is that it should store the Area value in the table when green is above Red. It should also store the negative value for area below the Red.

Both values should be displayed individually. I dont want to subtract the both areas at the moment. i just want to store the values individually and see the area above and below.

Re: areaundercurve

altenbach — Sat, 28 May 2011 17:38:59 GMT

What should be in the table? The incremental area with each iteration or only the summary whenever the difference changes sign?

Re: areaundercurve

weeke — Sat, 28 May 2011 17:44:35 GMT

The table should only show the summary when the sign is changed i.e the total area in that curve until when the sign is changed.

Re: areaundercurve

altenbach — Sat, 28 May 2011 17:56:29 GMT

What should happen if the difference temporarily goes to zero and the sign does not change?

Do you want one table entry for each segment or just the overall summary?

Here's a version that accumuates the above and below areas seperately and displays them in a table.

Re: areaundercurve

weeke — Sat, 28 May 2011 18:17:35 GMT

This is fine

But it would be better if the values donot increment with the current value.

The previous value should store and the next value should go in the second row and so on (not increment with the previous value).

Re: areaundercurve

weeke — Mon, 30 May 2011 06:52:13 GMT

Altenbach

I am pretty new to labview and its process, so very sorry for the inconvenience.

I just modified your VI little for my application. I am trying to take the ratio of below curve over above curve.

What i am unable to figure out is to store the values for both above and below in the table (is it using shift registers?) and i want to take the average of those values when i Stop the VI.

Thanks

Re: areaundercurve

altenbach — Mon, 30 May 2011 17:05:29 GMT

Maybe like this?

Re: areaundercurve

galoper — Mon, 30 May 2011 17:44:45 GMT

Can you please give me an idea how to store the values in a way that if i change the slider position, the new values for above and below should continue in the next rows and so on. They should not continue with the previous values as in this case where the values increment with the previous value.

Thanks

Re: areaundercurve

Cody C — Tue, 31 May 2011 21:20:11 GMT

Good Afternoon galoper,

Do you mean you would like to write the values out to a spreadsheet or some other source where you can view logged data once you are done running the code?

-Cody C

Re: areaundercurve

weeke — Wed, 01 Jun 2011 14:33:05 GMT

The new values should store in the same table. They should not add to the existing values.

New values should go into the next rows and so on

Re: areaundercurve

altenbach — Wed, 01 Jun 2011 16:10:30 GMT

Do you want a new table vaule for each consecutive segment with the same sign? How long will this run? Will the table contain millions of values after a while?

Re: areaundercurve

weeke — Wed, 01 Jun 2011 17:53:26 GMT

What you have done already is that in the columns for Above area and Below area, new values add into the existing values.

When you change the slider position, the next value for above and below area should go in the next rows and should not add up.

Yes the table is gonna contain a lot of values unless i stop the VI

Re: areaundercurve

weeke — Wed, 01 Jun 2011 17:57:18 GMT

the table will needs to be the same one

Re: areaundercurve

altenbach — Wed, 01 Jun 2011 18:08:47 GMT

@weeke wrote:

the table will needs to be the same one

same as what?