zvals.default: zvals.default function
Description
Default method for extracting 'z values' looks for $Zm, $Z, $z in that order.
See Also
xvals, yvals, zvals, xvals.default, yvals.default, xvals.fromXYZ, yvals.fromXYZ, zvals.fromXYZ, xvals.SpatialGridDataFrame, yvals.SpatialGridDataFrame, zvals.SpatialGridDataFrame