This function is generic.
Particular methods exist for the following objects:
[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
threshold(...)imwd.object, imwdc.object, irregwd object, threshold.imwd, threshold.imwdc, threshold.irregwd, threshold.wd, threshold.wd3D, threshold.wp, threshold.wst wd.object, wd3D.object, wp.object, wst.object.