Automatically retrieving some elements from a list

*To*: mathgroup at smc.vnet.net*Subject*: [mg128972] Automatically retrieving some elements from a list*From*: "Eduardo M. A. M. Mendes" <emammendes at gmail.com>*Date*: Thu, 6 Dec 2012 04:58:53 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Hello I wonder whether someone could help to understand what is behind Mathematica syntax. Here is an example: Control`ZeroPoleGainModel[TransferFunctionModel[s+1,s]] Control`ZeroPoleGainModel[{{{{-1}}},{},{{1}}},s] I need to extract some values of it so that the output is {{-1},{},{1}} Control`ZeroPoleGainModel[TransferFunctionModel[{{2/(1+s^2),s/(s-1)}},s]] Control`ZeroPoleGainModel[{{{{},{0}}},{{{-I,I},{1}}},{{2,1}}},s] The same thing but the output should be {{{},{0}},{{-l,I},{1}},{2,1}} Can a function be written to accomplish the above outputs automatically? BTW, is there a command to see all the functions under Control`? Many thanks Ed