[R-sig-Geo] iterative field naming

[Edzer Pebesma]

Jordan, please try

   zmbpts[[myfname]] <- extr$band1

On 12/29/2011 12:19 AM, Jordan Chamberlin wrote:
> Dear people,
> 
> Apologies in advance for what must be a silly question:  I want to
> iterative add a field to a dataframe, where the field takes a name that
> is created as part of the iteration. In the bit of code below, the
> problem line is "zmbpts$myfname <- extr$band1" : what I want to do is
> have the value of the string "myfname" be used as the name of the new
> field (rather than creating a new field called "myfname", which is what
> I'm doing).
> 
> for (i in 2000:2009) {
>     for (j in 1:12) {
> 
>         #temporarily go to data directory, grab file, then return to
> working directory
>         setwd(mydd)
>         myingrid <- gsub("( )", "", paste("pre", i, "_", j))
>         tmpgrid <- readGDAL(myingrid)
>         setwd(mywd)
> 
>         #create SpatialPixelsDataFrame
>         spdf <- as(tmpgrid, "SpatialPixelsDataFrame")
>          #summary(spdf)
>          #image(spdf, "band1", axes=TRUE, col=terrain.colors(20))
> 
>         #extract values to points
>         proj4string(spdf)<-proj4string(zmbpts)
>         extr = over(zmbpts,spdf)
> 
>         #add extracted values to SpatialPointsDataFrame
>         myfname <- gsub("( )", "", paste("y", i, "m", j))
>         zmbpts$myfname <- extr$band1
> 
>     }
> }
> 
> Thanks for your kind help!  Jordan
> 
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-- 
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