Hello:
I note a conflict in the documentation for Intamap/interpolate(), need
to know how to resolve:
I have two SpatalPointsDataFrame objects:
growingDegreeObservations <- readShapePoints("OhioGDDStationsGP.shp")
# computed surface phenomena, for individual lat/lon points
OrgStaLocs <- readShapePoints("Org_Locations.shp")
# species observation stations, for DIFFERENT lat/lon points
# Objective: Interpolate the growingDegree points into a SpatialGrid (?)
raster field, and then
# overlay the observation stations on to the field, and assign field
values to each observation station points
# according to intamap documentation, the interpolate() method accepts
two SptatialPointsDataFrame objects, interpolates
# the first ($value field) into a grid, and assigns interpolated
observations to the predicted locations (monarchStaLocs).
interpImage <- interpolate(growingDegreeObservations
,OrgStaLocs,list(mean=TRUE, variance=TRUE))
However, when this line is executed, the error occurs:
Error in function (classes, fdef, mtable) :
unable to find an inherited method for function "interpolate", for
signature "SpatialPointsDataFrame"
I guess that this refers to the first argument, and that the argument
must be a SpatialPixels or SpatialGrid data frame.
Questions:
1) Do I understand the inputs and outputs of interpolate() correctly?
2) How best to transform the incorrect (SpatialPointsDataFrame) argument
to match the required inputs? E.G., create the interpolated
SpatialPixelsDataFrame
of observations before calling interpolate())
3) Is there a better R technique (e.g., direct call to krige()) for
computing my solution?
Thanks, Rick R
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