Sean Davis wrote: > I have data in the form of (x,y) pairs and would like to find local > minima and maxima (typically the zeros of the 2nd derivative) of the y > values. I looked at numericDeriv, but I don't have an "expression" per > se. I looked at optim, also, but it looks like it will find only one > "global" max or min. I can code up my own piecewise derivatives, but > wondered if there is an existing function to do this.
If you don't have derivatives, and you don't have an expression, and you don't have a criteria how to minimize, please tell me of any known method that can handle your problem well enough. You could look whether y[i-1] <y[i] and y[i+1]<y[i] if y is ordered according to x, if this most trivial and very non-robust method fits to your definition... Uwe Ligges > Thanks, > Sean > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
