Message-ID: <AANLkTinhdgCHU7qUfZcN=5R_T2Nk7bRhuNkpN0c8rC0A@mail.gmail.com>
Date: 2011-03-25T16:42:13Z
From: Robert J. Hijmans
Subject: raster::extract NAs introduced?
In-Reply-To: <AANLkTinScGDCLcOY5cDYQH2u0eDwz+6P+pE9yjjYpSAP@mail.gmail.com>
Agus,
> any(is.na(SGRGBF40))
returns a RasterLayer with
> min value ? : 0
> max value ? : 1
TRUE == 1, so there is at least one NA value
also see:
count(SGRGBF40, NA)
summary(SGRGBF40, maxsamp=ncell(SGRGBF40))
Best, Robert
On Fri, Mar 25, 2011 at 6:58 AM, Agustin Lobo <alobolistas at gmail.com> wrote:
> Hi
>
> I've found that extract() introduces NAs:
> SGRGBF40 = brick("/media/Iomega_HDD/UAVetal/CALIBRACIONRADIOM/TESTCASA/CALSEL/SGRGB/SGRGBWBPS125F40.tif")
> calibf2 = readOGR(dsn="/media/Iomega_HDD/UAVetal/CALIBRACIONRADIOM/TESTCASA/CALSEL",layer="calibf2",stringsAsFactors=F)
> projection(SGRGBF40) = projection(calibf2)
> plot(subset(SGRGBF40,1))
> plot(calibf2,add=T)
> (overlay is ok now)
>
>> summary(SGRGBF40)
> Cells: ?4646400
> NAs ?: ?0 0 0
>
> ? ? ? ? ? ?1 ? ? 2 ? ? 3
> Min. ? ? 2629 ? ? 3 ? ? 3
> 1st Qu. 34100 22200 18290
> Median ?42470 27480 24680
> Mean ? ?40900 28510 25360
> 3rd Qu. 48360 33100 29010
> Max. ? ?65510 65510 64300
> summary based on a sample of 5000 cells, which is 0.107610192837466 %
> of all cells
> To make sure (NAs could outside the sample):
>> any(is.na(SGRGBF40))
> class ? ? ? : RasterLayer
> dimensions ?: 1760, 2640, 1 ?(nrow, ncol, nlayers)
> resolution ?: 1, 1 ?(x, y)
> extent ? ? ?: 0, 2640, -1759, 1 ?(xmin, xmax, ymin, ymax)
> projection ?: +proj=utm +zone=31 +ellps=intl +units=m +no_defs
> values ? ? ?: in memory
> min value ? : 0
> max value ? : 1
> So no NAs
> But:
>> summary(v)
> ?SGRGBWBPS125F40_1 SGRGBWBPS125F40_2 SGRGBWBPS125F40_3
> ?Min. ? :18444 ? ? Min. ? : ?119.4 ? Min. ? : ? ?3
> ?1st Qu.:33227 ? ? 1st Qu.:25516.4 ? 1st Qu.:15633
> ?Median :37752 ? ? Median :36264.1 ? Median :22374
> ?Mean ? :40208 ? ? Mean ? :36275.1 ? Mean ? :29737
> ?3rd Qu.:46899 ? ? 3rd Qu.:48052.5 ? 3rd Qu.:48116
> ?Max. ? :64992 ? ? Max. ? :63667.1 ? Max. ? :63826
> ?NA's ? : ? ?5 ? ? NA's ? : ? ?1.0
>
>
> Any explanation to this? Not a big problem (can use na.rm) but I'm
> concerned on this problem implying
> the means not being correct.
>
> Agus
>