Can't find the original. Here's a simple file to play with, real poles only, no zeros.
*pzexample.net *3 real poles, no zeros r1 1 2 1k c1 2 0 1u r2 2 3 10k c2 3 0 100n r3 3 4 100k c3 4 0 1n v 1 0 dc 0 ac 1 .pz 1 0 4 0 vol pz .print pz all .endThis is what it does in Berkeley 3f:
-- Circuit: *pzexample.net Date: Sun Mar 17 11:48:01 2013
*pzexample.net Pole-Zero Analysis Sun Mar 17 11:48:01 2013-------------------------------------------------------------------------------- Index pole(1) pole(2)
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0 -1.011111e+04, 0.000000e+00 -1.363589e+03, 0.000000e+00 *pzexample.net Pole-Zero Analysis Sun Mar 17 11:48:01 2013-------------------------------------------------------------------------------- Index pole(3)
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0 -7.252998e+02, 0.000000e+00CPU time since last call: 0.040 seconds.
Total CPU time: 0.040 seconds.
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)