 [b,a] = butter(3,
??? [b,a] = butter(3,
                     |
Missing variable or function.

 [b,a]=butter(3,0.001,'high')

b =

   0.99686333569707  -2.99059000709123   2.99059000709123  -0.99686333569707


a =

   1.00000000000000  -2.99371681727665   2.98745335824285  -0.99373651005710

 [b,a]=butter(3,0.00125,'high')

b =

   0.99608070721475  -2.98824212164424   2.98824212164424  -0.99608070721475


a =

   1.00000000000000  -2.99214602341255   2.98432285901999  -0.99217677528543

 [b,a]=butter(3,0.0015,'high')

b =

   0.99529869256428  -2.98589607769284   2.98589607769284  -0.99529869256428


a =

   1.00000000000000  -2.99057523075956   2.98119482233452  -0.99061948742017

 [b,a]=butter(3,0.00175,'high')

b =

   0.99451729114425  -2.98355187343276   2.98355187343276  -0.99451729114425


a =

   1.00000000000000  -2.98900443955990   2.97806924720923  -0.98906464238490

 [b,a]=butter(3,0.002,'high')

b =

   0.99373650235399  -2.98120950706196   2.98120950706196  -0.99373650235399


a =

   1.00000000000000  -2.98743365005572   2.97494613266544  -0.98751223611074

 [b,a]=butter(3,0.003,'high')

b =

   0.99061946150332  -2.97185838450995   2.97185838450995  -0.99061946150332


a =

   1.00000000000000  -2.98115051383676   2.96247826068066  -0.98132691750911

 [b,a]=butter(3,0.004,'high')

b =

   0.98751217486959  -2.96253652460877   2.96253652460877  -0.98751217486959


a =

   1.00000000000000  -2.97486742411365   2.95004967932747  -0.97518029551561

 [b,a]=butter(3,0.005,'high')

b =

   0.98441460436789  -2.95324381310366   2.95324381310366  -0.98441460436789


a =

   1.00000000000000  -2.96858439637183   2.93766032527870  -0.96907211329255

 