Numeric Integration of positive and negative values in the same signal

Question

Hello.. I need to perform an evaluation of Area Under Curve of my signal, but it contains positive and negative values. I am using the "Numeric Integration" function, but the result expressed by my VI represent: AREA OF POSITIVE VALUES - AREA OF NEGATIVE VALUES, in other words, my result represent the difference between these two areas. But I want to know the total area, the sum of positive values area and negative values area, and because both values has are "+", my final result should has "+" notation.
For example:
Area of positive values: +45.00
Area of negative values: +34.00
Total area: +79.00
How do I modify my VI to obtain the total area value?
I try to split my values in two parts:
A) only the positive and zero values
B) only the negative values
I calculated the areas of both splits and performed an sum of them, but the final result does not matches with total area (computed by another software to know the real value)
I attached an picture of my VI
Thank you
Daniel
Attachments:
Numeric Integration1.png ‏12 KB

Answer 1

Use an event structure for the boolean value changed. You also did not follow Lynn's advice to insert an "absolute value". It would really simplify everything.
Here's how it would look in a newer version of LabVIEW (your icons look different because you have an older version. The functions are the similar).
This is just a draft and the program needs to be improved. Use a state machine with events for read file and another for value change on the sampling rate. Place the data array in a shift so you can change the sampling rate without the need to re-read the file. Modify as needed. 
Some important pointers in general:
There is NO need to constantly spin the loop every nanosecond. The only time the loop needs to spin if if one of the inputs has changed.
If you don't use an event structure, all UI loops need a wait to conserve CPU.
Never (almost never) use "switch until released". Typically you want to use "latch when released" which makes the terminal true exactly once until the value is read and it will revert to false after that. "switch until released acts like a doorbell, so if it werent for the file dialog, you would execute the case several times in a row.
You don't need to get the array size and wire N of the FOR loop if you are autoindexing. LabVIEW will spin the loop until it runs out of elements automatically.
There is an atomic operation for "negate" in the numeric palette. No need to multiply with a "-1" diagram constant.
There is an atomic operation for ">=0" in the comparison palette. No need to compare with a "0" diagram constant.
Use a stop button on the loop termination.
Everything that only needs to be done once after the file is read (e.g. you inner loop, etc. also belongs inside the case structure. Right?
In general, you would make things much easier for us if you would attach your actual live VI instead of dead images.
Message Edited by altenbach on 04-19-2008 12:22 PM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
areaPositive.png ‏9 KB