[R-sig-Geo] interpolation with missing values
Edzer Pebesma
edzer.pebesma at uni-muenster.de
Wed Apr 17 19:53:05 CEST 2013
On 04/17/2013 07:09 PM, Barry Rowlingson wrote:
> On Wed, Apr 17, 2013 at 4:35 PM, mauvela <mauricioandresvela at gmail.com> wrote:
>> I need to interpolate some data about PM10 for some location (schools). I
>> have daily data and about 50 stations. I have to interpolate for every day
>> but my problems comes with the missing values of many stations in many days.
>> For example for one day I could have data for 10 stations while for other
>> day data from 50. When ignoring these missing data and interpolating using
>> ordinary kriging for each day, the results for each school varies a lot
>> depending of which stations have available data. For example a school near
>> one station changes a lot when that station have missing in one day. What
>> should be the best way to deal with this missing values, is there a method
>> for imputation that takes into account the temporal and the spatial
>> variability of the data?
>
> Off the top of my head, do multiple imputations of the missing values
> based on the mean and sd of the values at that site when not missing.
> You'll then end up with a number (100, say) of kriged maps. You can
> probably then take the mean over those as your map and for the
> variance you'll have to combine the kriging variance with the
> imputation variance...
>
> This is probably valid assuming the dropouts are random... Also, it
> doesn't take into account any temporal correlation which might get you
> a better estimate of your imputed values...
>
> What you do may also depend on what you are doing with the data. If
> its just to produce pretty maps, then you might not need something so
> sophisticated. If you are computing the number of days that PM10 in
> some location exceeds some threshold, then you may have to give it
> some more thought...
>
Maybe try spatio-temporal interpolation?
--
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics e.pebesma at wwu.de
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