[R] Question re: interpolation

Jessica Schedlbauer jschedlb at fiu.edu
Mon May 3 02:47:46 CEST 2010

Thanks to all for their answers so far - the following suggestion comes close to what I was looking for, but perhaps I was not clear enough in my initial message.

Following the example below, I'd like to be able to interpolate in such a way that considers adjacent datapoints in both columns and rows, rather than just the datapoints appearing in rows.  Is this possible?


From: Felipe Carrillo [mazatlanmexico at yahoo.com]
Sent: Sunday, May 02, 2010 5:53 PM
To: Jessica Schedlbauer; r-help at r-project.org
Subject: Re: [R] Question re: interpolation

Are you looking for something like this?

data <- data.frame(first= c(1,2,3,4,5,6,7,8), zehn = c(15,NA,NA,NA,NA,18,NA,25),
     second = c(4,NA,7,9,NA,10.2,NA,12),
    third= c(6,7,NA,NA,10,12,NA,16))
    data2 <-na.approx(data,na.rm=F)

Felipe D. Carrillo
Supervisory Fishery Biologist
Department of the Interior
US Fish & Wildlife Service
California, USA

----- Original Message ----
> From: Jessica Schedlbauer <jschedlb at fiu.edu>
> To: "r-help at r-project.org" <r-help at r-project.org>
> Sent: Sun, May 2, 2010 2:27:10 PM
> Subject: [R] Question re: interpolation
> Hello,

I have a matrix in which two variables, x and y, are used together
> to determine z.  The variables x and y are sorted into classes.
> Specifically, values for variable x range from 0 to 2.7 and are sorted into
> class increments of 0.15 and variable y ranges from 0-2100 with class increments
> of 100.  For each x-y class combination, I have calculated a mean value of
> z from existing data.  However there are gaps in the existing data (i.e.,
> x-y combinations for which there are no z data).  I would like to
> interpolate values to fill in these missing datapoints, but have so far been
> unable to find a straightforward way of doing so in R.  There are many gaps
> in the data and I need to repeat this process for several individual
> datasets.  That said, I am looking for a way to avoid interpolating each
> missing point separately.

Any suggestions would be greatly
> appreciated.

> Schedlbauer

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