# cubic spline

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## cubic spline

 Hallo, I'm facing a problem and I would really appreciate your support. I have to translate some Matalb code in R that I don't know very well but I would like to. I have to interpolate 5 point with a cubic spline function and then I expect my function returns the Y value as output a specific X value inside the evaluation range.  Let's suppose that:   1-  X = [-10, -5, 0, 5, 10]    2 - Y = [12, 10, 8, 7, 6]  3 - I have to interpolate with a cubic spline assuming x=11In Matlab I used this function: y = interp1(X, Y, x, "cubic"); How can I do the same in R? Many thanks in advance for your reply and support! Kindly Steve
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## Re: cubic spline

 Hi Steve, Check the "splint" function in the "fields" package. HTH, Jorge.- On Sat, Dec 1, 2012 at 11:09 PM, Steve Stephenson <> wrote: > Hallo, > I'm facing a problem and I would really appreciate your support. > I have to translate some Matalb code in R that I don't know very well but I > would like to. > I have to interpolate 5 point with a cubic spline function and then I > expect > my function returns the Y value as output a specific X value inside the > evaluation range.  Let's suppose that: >   1-  *X = [-10, -5, 0, 5, 10]* >   2 - *Y = [12, 10, 8, 7, 6]* >   3 - *I have to interpolate with a cubic spline assuming x=11* > > In Matlab I used this function: > > *y = interp1(X, Y, x, "cubic"); * > > How can I do the same in R? > Many thanks in advance for your reply and support! > Kindly > > Steve > > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/cubic-spline-tp4651537.html> Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help> PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html> and provide commented, minimal, self-contained, reproducible code. >         [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: cubic spline

 Hi Jorge, many thanks for your suggestion! I tried the function you mentioned and it looks working!! Now I have just to check that splint (R) and interp1 (Matlab) functions provide me the same results. Kind regards! Steve
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## Re: cubic spline

 In reply to this post by Steve Stephenson On Dec 1, 2012, at 5:09 AM, Steve Stephenson wrote: > Hallo, > I'm facing a problem and I would really appreciate your support. > I have to translate some Matalb code in R that I don't know very   > well but I > would like to. > I have to interpolate 5 point with a cubic spline function and then   > I expect > my function returns the Y value as output a specific X value inside   > the > evaluation range.  Let's suppose that: >  1-  *X = [-10, -5, 0, 5, 10]* >  2 - *Y = [12, 10, 8, 7, 6]* >  3 - *I have to interpolate with a cubic spline assuming x=11* > > In Matlab I used this function: > > *y = interp1(X, Y, x, "cubic"); * > > How can I do the same in R? > Many thanks in advance for your reply and support! splinefun( x = c(-10, -5, 0, 5, 10),             y = c(12, 10, 8, 7, 6),           method="natural")(11) [1] 5.785714 -- David Winsemius, MD Alameda, CA, USA ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: cubic spline

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## Re: cubic spline

 Martin Maechler stat.math.ethz.ch> writes:  [snip] > but definitely *no* need to use a function from an extra CRAN > package .. as someone else ``erronously'' suggested. > > Note that >   spline() and splinefun() > together with >   approx() and approxfun() > are among the several hundred functions that were already > part of "pre-alpha" R, i.e., before R had a version number or *any* > packages ... > and yes, the README then started with the two lines > > | R Source Code (Tue Jun 20 14:33:47 NZST 1995) > | Copyright 1993, 1994, 1995 by Robert Gentleman and Ross Ihaka > > and it would be *really* *really* great > if people did not add stuff to their packages that has > been part of R for longer than they have even heard of R. > > Martin Maechler, ETH Zurich   To be fair, the 'fields' package has a pretty long history too -- I think it may have been ported from an S-PLUS 'package' (or whatever the correct terminology is) that existed quite a while ago.  I think it was the FUNFITS module. From http://lib.stat.cmu.edu/S/:funfits     FUNFITS is a comprehensive S-Plus module for fitting functions and nonlinear time series, including multivariate splines, Kriging and neural networks.  Contributed by Doug Nychka ([hidden email]). [25/Apr/96] [24/Mar/97][24/Sep/99] (3 kbytes). The actual compressed tar file is available as funfits23.tar.gz in the S collection. Access this file via FTP, or the WWW, but not e-mail. (596k).  Older version avaulable at funfits.tar.Z   A quick look at funfits.tar.Z suggests that 'splint' existed in that version, in 1996 -- so respectably old. ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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