Fast way to find the number of non-zero terms in an array or image

Question

I am trying to use the Standard Deviation PtbyPt Vi.  It takes in a series of points, can be reset when beginning the calculation.  There is also an input for sample size.  I am calculating some statistics on an array...and would only  to include like the non-zero elements that are  in the sample. 
Is there a quick way to look at an array and find the number of non-zero elements?
Thanks.
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Answer 1

GerdW wrote:
- for big arrays this may lead to "out of memory" problems because of creation of data copies
Here's a quick rundown on memory allocations based on the algorithm.
(case 1&3)
If you do the "!=0, ?1:0, I32, sum" shuffle, each step needs to allocate a new array, so if the input array is DBL and uses N amount of memory, we need 7N/8 more memory.
(Total of 15N/8, or 13N/8 if we don't need the I32, but in this case the array are too small to worry about anything )
The nice thing is that it works for any array dimensionality (1D, 2D, 5D, etc...)
(Case 2&5)
If you do the summing in a shift register, No additional array memory is needed. Unfortunately, the code needs to be changed by adding an extra FOR loop for each dimension (see case 5 for 2D inputs).
(Case 4)
If we reshape the N-D array to a 1D array, we need to create a second copy, so the memory usage is about twice. This also works for any dimension.
In real life, and if memory is a potential issue, you should always do some benchmarks.
Often, the issues are more complex, so this is just a quick summary.
Message Edited by altenbach on 10-23-2008 11:59 AM
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