[R-sig-Geo] Conditional operations and rasters

Andrew Vitale vitale232 at gmail.com
Wed Sep 16 05:47:32 CEST 2015

```I would do something like the following:

library(raster)

lai <- raster(ncols=50, nrows=50)
lai[] <- 1:ncell(lai)

emmiss_0_func <- function(lai) {
emmiss_0 <- ifelse((lai < 1000), (0.95 + (0.01 * lai)), 0.95)
return(emmiss_0)
}
emmiss_nb_func <- function(lai) {
emmiss_nb <- ifelse((lai < 1000), (0.97 + (0.0033 * lai)), 0.98)
return(emmiss_nb)
}

emiss <- stack(calc(lai, emmiss_0_func), calc(lai, emmiss_nb_func))
plot(emiss)

On Tue, Sep 15, 2015 at 8:30 PM, Vijay Lulla <vijaylulla at gmail.com> wrote:

> I have no idea what you're trying to accomplish with your program
> logic but I think the below might work for you.
>
> R> lai <- raster(ncols=360,nros=180)
> R> lai[] <- 1:ncell(lai)
>
> R> idx <- lai < 1000
> R> emiss_0 <- lai
> R> emiss_0[] <- 0.95
> R> emiss_0[idx] <- 0.95 + (lai[idx]*0.01)
>
> R> emiss_nb <- lai
> R> emiss_nb[] <- 0.98
> R> emiss_nb[!idx] <- 0.97+(lai[!idx]*0.0033)
> R> ?Which # from raster package
>
> Other gurus on the list might suggest more efficient way[s] of doing this.
>
> HTH,
> Vijay.
>
> On Tue, Sep 15, 2015 at 10:51 PM, Thiago V. dos Santos
> <thi_veloso at yahoo.com.br> wrote:
> > Hi all,
> >
> > This is probably a silly question, but I could not find an appropriate
> >
> > I am trying create a raster based on conditional statements applied on
> an original raster.
> >
> > This is some sample code:
> >
> > lai <- raster(ncols=360, nrows=180)
> > lai[] <- 1:ncell(lai)
> >
> > if (lai < 1000) {
> >
> >     emiss_0  <- 0.95 + (0.01 * lai)
> >     emiss_nb <- 0.97 + (0.0033 * lai)
> >
> >
> > } else if (lai >= 1000) {
> >
> >
> >     emiss_0  <- 0.95
> >     emiss_nb <- 0.98
> >
> >
> > }
> >
> > Error in if (lai < 3) { : argument is not interpretable as logical
> >
> >
> > What would be the right way to do that?
> >  Greetings,
> >  -- Thiago V. dos Santos
> >
> > PhD student
> > Land and Atmospheric Science
> > University of Minnesota
> >
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
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>

--
*Andrew P. Vitale*
Staff Research Scientist
Desert Research Institute
2215 Raggio Pkwy
Reno, NV 89512

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