Point-by-Point Analysis and Array-Based Analysis in LabVIEW

The approach used for most point-by-point analysis operations in LabVIEW remains the same as array-based analysis. You can use filters, integration, mean value algorithms, and so on, in the same situations and for the same reasons that you can use these operations in array-based data analysis. In contrast, the computation of zeros in polynomial functions is not relevant to point-by-point analysis, and point-by-point versions of these array-based VIs are not necessary.

The following table compares array-based LabVIEW analysis to point-by-point analysis.

Data Analysis Technology
Array-Based Analysis (traditional paradigm) Prepare a buffer unit of data. Analyze data. Produce a buffer of analyzed data. Generate report.	Point-By-Point Analysis (newer paradigm) Receive continuous stream of data. Filter and analyze data continuously. Generate real-time events and reports continuously.

The following table presents other comparisons between array-based and point-by-point analysis.

Characteristic	Array-Based Analysis	Data Acquisition and Analysis with Point By Point VIs
Compatibility	Limited compatibility with real-time systems	Compatible with real-time systems; backward compatible with array-based systems
Data typing	Array-oriented	Scalar-oriented
Interruptions	Interruptions critical	Interruptions tolerated
Operation	You observe, offline	You control, online
Performance and programming	Compensate for startup data loss (4-5 seconds) with complex �state machines�	Startup data loss does not occur; initialize the data acquisition system once and run continuously
Point of view	Reflection of a process, like a mirror	Direct, natural flow of a process
Programming	Specify a buffer	No explicit buffers
Results	Output a report	Output a report and an event in real time
Run-time behavior	Delayed processing	Real time
Run-time behavior	Stop	Continue
Run-time behavior	Wait	Now
Work style	Asynchronous	Synchronous

When you perform point-by-point analysis, keep in mind the following concepts:

• Initialization�You must initialize the point-by-point analysis application to prevent interference from settings you made in previous sessions of data analysis.
• Reentrant Execution�You must enable LabVIEW reentrant execution for point-by-point analysis. Reentrant execution allocates fixed memory to a single analysis process, guaranteeing that two processes that use the same analysis function never interfere with each other.

  Note   If you create custom VIs to use in a point-by-point application, be sure to enable reentrant execution. Reentrant execution is enabled by default in almost all Point By Point VIs.

• Deterministic Performance�Point-by-point analysis is the natural companion to many deterministic systems, because it efficiently integrates with the flow of a real-time data signal.