Burrough, P. A., and McDonell, R. A., 1998. Principles of Geographical Information Systems (Oxford University Press, New York)
spatial(x, slope = TRUE, aspect = TRUE)
x | A matrix for spatial data with row for longitude and column for latitude. dimnames must be specified for values of longitude and latitude |
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slope | Logical, whether return slope |
aspect | Logical, whether return aspect |