This routine is used to remove points that are of a specified material type.  Elements with the specified material types are flagged by setting the element material type negative.  After using rmmat, rmpoints/compress will delete elements whose material type is negative and the dudded nodes.
rmmat/material number/[all|node|element]/[exclusive]
default is: rmmat/material number or rmmat/material number/all
removes nodes with imt = material number and removes elements with itetclr= material number

other options are:

rmmat/material number/node
removes nodes  with imt = material number

rmmat/material number/element
removes elements with itetclr= material number

rmmat/material number//exclusive or rmmat/material number/all/exclusive
removes everything except nodes with imt =material and removes everything except elements with itetclr= material

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