MODIS/man/makeWeights.Rd

% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/makeWeights.R
\name{extractBits}
\alias{extractBits}
\alias{makeWeights}
\alias{maskWater}
\title{Extract Bit-Encoded Information and Create Weights Raster}
\usage{
extractBits(x, bitShift = 2, bitMask = 15, filename = "", ...)

makeWeights(x, bitShift = 2, bitMask = 15, threshold = NULL,
  filename = "", decodeOnly = FALSE, ...)

maskWater(X, bitShift = NULL, bitMask = NULL, keep = NULL,
  datatype = "INT1U", ...)
}
\arguments{
\item{x}{\code{matrix}, vector or \code{Raster*} object.}

\item{bitShift}{\code{integer}. Bit starting point, see examples and 
\code{\link{detectBitInfo}}.}

\item{bitMask}{\code{integer}. Bit mask size, see examples and 
\code{\link{detectBitInfo}}.}

\item{filename}{\code{character} passed to \code{\link{writeRaster}}. If not 
specified, output is written to a temporary file.}

\item{...}{Other arguments passed to \code{\link{writeRaster}}.}

\item{threshold}{\code{integer}. Threshold for valid quality.}

\item{decodeOnly}{\code{logical}. If \code{FALSE} (default), convert bits to 
weights from 0 (not used) to 1 (best quality). If \code{TRUE}, only extract 
selected bits and convert to decimal system.}

\item{X}{\code{Raster*} object.}

\item{keep}{If \code{NULL} (default), bits are only encoded, else an 
\code{integer} vector of values you want to keep (becomes \code{TRUE}), the 
rest becomes \code{NA}. See examples.}

\item{datatype}{\code{character}. Output datatype, see 
\code{\link{writeRaster}}.}
}
\value{
A \code{Raster*} object.
}
\description{
This function applies \code{\link{bitAnd}} and \code{\link{bitShiftR}} 
from \strong{bitops} to convert bit-encoded information. It is also possible 
to convert this information to a scale from 0 to 1 in order to use it as 
weighting information in functions like \code{\link{whittaker.raster}} or 
\code{\link{smooth.spline.raster}}.
}
\section{Functions}{
\itemize{
\item \code{extractBits}: Extract bit-encoded information from \code{Raster*} file

\item \code{maskWater}: Masks water (additional information required)
}}

\note{
\code{\link{makeWeights}} and \code{\link{extractBits}} are identical with 
the only difference that \code{\link{makeWeights}} does additionally convert 
the data into weighting information.
}
\examples{
\dontrun{

# example MOD13Q1 see https://lpdaac.usgs.gov/products/modis_products_table/mod13q1 
# enter in Layers
# See in TABLE 2: MOD13Q1 VI Quality
# column 1 (bit) row 2 VI usefulness 
bitShift = 2
bitMask = 15 # ('15' is the decimal of the binary '1111')  
# or try to use
detectBitInfo("MOD13Q1") # not all products are available!
viu <- detectBitInfo("MOD13Q1","VI usefulness") # not all products are available!
viu

# simulate bit info
bit <- round(runif(10*10,1,65536))

# extract from vector
makeWeights(bit,bitShift,bitMask,decodeOnly=TRUE)
# the same as
extractBits(bit,bitShift,bitMask)

# create a Raster object
VIqual <- raster(ncol=10,nrow=10)
VIqual[] <- bit

# extract from Raster object
a <- makeWeights(VIqual,bitShift,bitMask,decodeOnly=TRUE)

# linear conversion of 0 (0000) to 15 (1111) to 1 fo 0 
b <- makeWeights(VIqual,bitShift,bitMask,decodeOnly=FALSE)

threshold=6 # every thing < threshold becomes a weight = 0
c <- makeWeights(VIqual,bitShift,bitMask,threshold,decodeOnly=FALSE)

res <- round(cbind(a[],b[],c[]),2)
colnames(res) <- c("ORIG","Weight","WeightThreshold") 
res

#####
# water mask
tif = runGdal(product="MOD13A2",begin="2009001",end="2009001", extent=extent(c(-9,-3 ,54,58)),
              SDSstring="001",job="delme") # 6.4 MB
x <- raster(unlist(tif))

res1 <- maskWater(x)
plot(res1)

res2 <- maskWater(x,keep=1) # 1 = Land (nothing else)
x11()
plot(res2)

# Land (Nothing else but land) + Ocean coastlines and lake shorelines + shallow inland Water,
# the rest becomes NA
x11()
res3 <- maskWater(x,keep=c(1,2,3)) 
plot(res3)

###############

# as on Linux you can read HDF4 directly you can also do:
if(.Platform$OS.type=="unix")
{
  x <- getHdf(HdfName="MOD13A2.A2009001.h17v03.005.2009020044109.hdf", wait=0) # 6.4 MB
  
  detectBitInfo(x) # just info
  getSds(x) # just info
  
  x <- getSds(x)$SDS4gdal[3] # you need 'VI Quality'
  x  <- raster(x) 
  # plot(x)
  # ex <- drawExtent()
  ex <- extent(c(-580779,-200911,5974929,6529959))
  x  <- crop(x,ex) # just for speed-up
  
  res1 <- maskWater(x)
  plot(res1)
  
  res2 <- maskWater(x,keep=1) # 1 = Land (Nothing else but land), the rest becomes NA
  x11()
  plot(res2)
  
  # Land (Nothing else but land) + Ocean coastlines and lake shorelines + shallow inland Water,
  # the rest becomes NA
  res3 <- maskWater(x,keep=c(1,2,3))
  x11()
  plot(res3)
}
}

}
\seealso{
\code{\link{detectBitInfo}}.
}
\author{
Matteo Mattiuzzi
}