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copied!<p><em>UPDATE : This problem is also discussed on the R mailing list, and it turned out to be a bug/inconsistency in the resolving of passed arguments in specific cases. This is reported to R. The discussion can be found at :</em> <a href="http://r.789695.n4.nabble.com/Passing-arguments-between-S4-methods-fails-within-a-function-bug-example-with-raster-package-td2339750.html" rel="nofollow noreferrer" title="archive of R mailing list">Nabble</a></p> <hr> <p>Quite an interesting problem. When you check</p> <pre><code>showMethods("xyValues",incl=T) </code></pre> <p>There are two important chunks of code. The one with signature vector for xy, and one for xy as a matrix. As your object is a "RasterLayer" object, you need to make sure origin.point is a matrix. This is pretty counterintuitive actually if we look at the code</p> <pre><code>object="Raster", xy="vector" function (object, xy, ...) { if (length(xy) == 2) { callGeneric(object, matrix(xy, ncol = 2), ...) } else { stop("xy coordinates should be a two-column matrix or data.frame, or a vector of two numbers.") } } </code></pre> <p>So this actually only transforms the xy argument to a matrix, and passes all other arguments to the next generic. The next one has to be this one then :</p> <pre><code>object="RasterLayer", xy="matrix" function (object, xy, ...) { .local <- function (object, xy, method = "simple", buffer = NULL, fun = NULL, na.rm = TRUE) { if (dim(xy)[2] != 2) { stop("xy has wrong dimensions; it should have 2 columns") } if (!is.null(buffer)) { return(.xyvBuf(object, xy, buffer, fun, na.rm = na.rm)) } if (method == "bilinear") { return(.bilinearValue(object, xy)) } else if (method == "simple") { cells <- cellFromXY(object, xy) return(.readCells(object, cells)) } else { stop("invalid method argument. Should be simple or bilinear.") } } .local(object, xy, ...) } </code></pre> <p>This one takes the argument "buffer". Why the value for the argument can't be found in the parse tree, I have no clue, but you could try to avoid the method cascade by giving a matrix as input instead of a vector.</p>

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