R help - Mar 2008 - differentiating a numeric vector

What functions exist for differentiating a numeric vector (in my case
spectral data)?  That is, experimental data without an analytical
function.  ie,
> x <- seq(1,10,0.1)
> y=x^3+rnorm(length(x),sd=0.01)     #although the real function would be
nothing simple like x^3...
> derivy <- ....
I know I could just use diff(y) but it would be nice to estimate
derivatives at the endpoints, calculate higher-order derivatives, and
maybe have some smoothing options ie by differentiating a spline or
something like that.

Have you looked at the 'fda' package?  It has many functions for 
doing what you want.  A strength is that it is a companion package for 
two books on that and related issues, and includes script files under 
"~R.installation.directory\library\fda\scripts" to reproduce some of
the
analyses.  It may include more than you want to consider, but for me, 
too much is usually better than nothing. 

      hope this helps. 
      Spencer Graves
p.s.  If you try it and have trouble, please submit another question 
including commented, minimal, self-contained, reproducible code, as 
requested in the posting guide 
http://www.R-project.org/posting-guide.html. 

Levi Waldron wrote:
> What functions exist for differentiating a numeric vector (in my case
> spectral data)?  That is, experimental data without an analytical
> function.  ie,
>
>   
>> x <- seq(1,10,0.1)
>> y=x^3+rnorm(length(x),sd=0.01)     #although the real function would be
nothing simple like x^3...
>> derivy <- ....
>>     
>
> I know I could just use diff(y) but it would be nice to estimate
> derivatives at the endpoints, calculate higher-order derivatives, and
> maybe have some smoothing options ie by differentiating a spline or
> something like that.
>
> ______________________________________________
> R-help at r-project.org 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.
>

Check out ?splinefun


On Wed, Mar 5, 2008 at 3:18 PM, Levi Waldron <leviwaldron at gmail.com>
wrote:
> What functions exist for differentiating a numeric vector (in my case
> spectral data)?  That is, experimental data without an analytical
> function.  ie,
>
> > x <- seq(1,10,0.1)
> > y=x^3+rnorm(length(x),sd=0.01)     #although the real function would
be nothing simple like x^3...
> > derivy <- ....
>
> I know I could just use diff(y) but it would be nice to estimate
> derivatives at the endpoints, calculate higher-order derivatives, and
> maybe have some smoothing options ie by differentiating a spline or
> something like that.
>
> ______________________________________________
> R-help at r-project.org 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.
>