```Date: Feb 12, 2013 2:16 PM
Author: Derek Goring
Subject: Re: second derivative

On Wednesday, February 13, 2013 5:07:20 AM UTC+13, winnie  wrote:> "aasim Azooz" <aasimazooz@yahoo.com> wrote in message <g2483i\$bfa\$1@fred.mathworks.com>...> > > > > > if y=f(x) then the first derivative is> > > y1=diff(y)./diff(x)> > > The second derivative is> > > y2=diff(y1)./diff(x)> > > don't forget that the size of y1 is less than the size of y > > > by one and the size of y2 is less than the size of y by two> > > > > > Aasim Azooz> > > > > > > Hi,> > > > I just looked into computing an approximate second derivative with Matlab and found the answer given by Aasim (above).> > > > However, shouldn't it rather be:> > y2=diff(y1)./diff(x^2) ?> > > > The answer Aasim gave comes up repeatedly (in similar form) in my web searches, hence I am not sure whether I am making a conceptual error here...> > My x values are equally spaced, in case that makes a difference.> > > > Thanks,> > WinnieYes, you are making a conceptual error.Aasim has the correct algorithm.
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