[R-sig-Geo] Modifying the length of a matrix variable

[r@i@1290 m@iii@g oii @im@com]

Hello there,
I am currently trying to modify a variable's length. It is called "Model4" and is a matrix. It currently has the length of 95, as per "length(Model4)". However, I would like to create a new Model4 (let's say "NewModel4"), in which it has a length of 90, instead of 95.
Is there a way to do this? 
Thanks, and any assistance would be greatly appreciated!  
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