derivative fit function

[marconi2005]

Hello

Is possibel make a fit and then make a derivative off this result function. And if it is, how i can do it.

Thanks

[ClementG]

Hi,

This is possible only if you have the Professional or full version of LabVIEW, and not available with the Base development system.

Best regards

[DFGray]

You really want a Savitzky-Golay filter.  Do a search on the forums for Savitzky-Golay and you will find many hits and code examples.  You can construct such a filter easily with any version of LabVIEW.  You can find the theory behind it in Numerical Recipes in C, second edition, by Press et. al.  It can be found in most libraries.

The Savitzky-Golay filter is a method of doing a least-squares polynomial fit to every point in your array using a simple convolution.  The output can be either a value of the polynomial or a derivative of the polynomial, depending upon how you calculate the convolution coefficients.

[JohnnyF]

Hi guys, I have a piggyback question. I have tried implimenting the Savitzky-Golay filters as found on http://www.sciware.com.au. The problem I have is that regardless of which version I use and how I handle the error in, I do not get any outputs for smoothed y and dy. I've experimented with all the inputs and get a constant zero output with an index of -1 when I use the point by point version. I've attached my code in the hopes that someone can point out my mistake. Please be gentle, I'm new at this. Thanks in advance for your help.