a data.frame with three columns (names are specified in the colnames argument) giving the x and y coordinates and the attribute values at the locations given by the grid data.
Arguments
data
grid data: either a grid data matrix, or a list with components data (a matrix with the grid data) and header (the grid header information); see read.ascii.grid() for details
header
optional list giving grid header information; see read.ascii.grid() for details
varname
character: name to be assigned to the column with the z values in the output data.frame
colnames
names to be given to the columns corresponding to the x and y coordinates and the grid variable in the output data.frame