[time-nuts] exponential+linear fit

Jim Lux jimlux at earthlink.net
Sat Oct 5 15:53:52 UTC 2013


On 10/5/13 8:47 AM, Tim Shoppa wrote:
> How slow of a processor are you working with? A modern PC using a general
> purpose graphing and fitting tool (e.g. gnuplot) will fit tens of thousands
> of points in a fraction of a second.
> http://people.duke.edu/~hpgavin/gnuplot.html
>
> If you want to do this in your own code, there are lots of least-squares
> fitting examples in every first year numerical analysis textbook in every
> computer language ever written (I learned this in FORTRAN 4 naturally).
> http://en.wikipedia.org/wiki/Least_squares
>
> If you have hardware substantially more primitive (e.g. a PIC, a bag of
> 2N2222's and 555's, etc.) you have to do the fit on, then it's an
> interesting problem :-)
>

In the future, more the latter than the former. 48 MHz ARM Cortex-M4, 
for instance.

For now, though, yeah, it's on a not very fast PC (Windows Experience 
Rating around 2), but compiled matlab does it very quickly.  But, given 
that sooner or later I'm going to be heading for a more resource 
constrained environment, or trying to FPGA it, I'm looking for simple 
algorithms to implement the simplified models.

And, of course, I don't want to drag in all the libraries that one gets 
with Matlab,Octave,gnuplot, etc.

They're great for figuring out what's going on and trying out the 
algorithms.









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