curve fitting toolbox

2011 3 18
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I'm programming in matlab and using curve fitting toolbox to fit my data. I need to evaluate the 1th derivative of my curve in some data point. Do you know how I can do it in my code? I need to use 'cubic spline (interpolant) fitting'.

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Sarah Wait Zaranek
Sarah Wait Zaranek 2011-3-18

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The curvefit object you get out of curvefitting tool will allow you to take a derivative at a point using the differentiate method.
See code below. I generated a fit using the command line but it is the same thing you can get out of the curvefitting toolbox.
load census
f2 = fit(cdate,pop,'cubicinterp');
fx = differentiate(f2, 0.2)

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Sarah Wait Zaranek
Sarah Wait Zaranek 2011-3-18
Aside -- your name and mine are quite similar.
SARAH ZAVAREH
SARAH ZAVAREH 2011-3-19
Great! Thank you.
But another duestion: Do you know how I can find in which points 1th derivative is equal to zero? (how we can solve first derivative equation?)
p.s. yeah our names are the same :D

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SARAH ZAVAREH
SARAH ZAVAREH 2011-3-21

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Do you know how I can find in which points 1th derivative is equal to zero? (how we can solve first derivative equation?)

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Sarah Wait Zaranek
Sarah Wait Zaranek 2011-3-22
If you have the optimization toolbox, fzero probably would be ideal.
http://www.mathworks.com/access/helpdesk/help/techdoc/ref/fzero.html
SARAH ZAVAREH
SARAH ZAVAREH 2011-3-29
Thanks alot for your useful helps :)

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