On 04/17/2013 07:09 PM, Barry Rowlingson wrote: > On Wed, Apr 17, 2013 at 4:35 PM, mauvela <mauricioandresv...@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.pebe...@wwu.de _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo