[R] Problems generating image from tiff file

Mehdi Khan mwkhan at ucdavis.edu
Fri Jul 17 01:02:43 CEST 2009


I imported the attached tiff file and converted the coordinate system to
long lat and graphed it:

californiatiff<- readGDAL("california1.tif")
proj4string(californiatiff)
> rasterprojection <- spTransform(californiatiff, CRS("+proj=longlat")

however, when using the plot command for rasterprojection, I get a blob.  I
can see the outline of the state of california and nevada, but rather than
being able to see the geographic features, it is just a monocolor blob.  My
suspicion is that since it is a list of coordinates and another column that
contains attributes, I need to turn it into a polygon.  I've tried the
following codes but none work:

> rasterprojection2<-SpatialPolygons(rasterprojection)
Error in is.vector(X) :
  trying to get slot "Polygons" from an object of a basic class ("integer")
with no slots

 rasterprojection2<- Polygons(rasterprojection)
Error in as.vector(x, "list") :
  cannot coerce type 'S4' to vector of type 'list'

Essentially, all I need to do is to connect the coordinates into polygons.
What am I doing wrong?

Thank you!


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