From Mark Widholm:
This plug-in allows MathPad users to run analog circuit simulations via the MacSpice application. The use of MathPad with MacSpice allows circuit simulation results to be combined with other mathematical models or data.
To make use of this plug-in you must have MathPad and MacSpice installed. Both are available for free.
MathPad is a general purpose math analysis and plotting program available at: pubpages.unh.edu/~mwidholm/MathPad MacSpice is a full implementation of the Berkeley Spice 3f5 electronic circuit simulator available at: newton.ex.ac.uk/teaching/CDHW/MacSpice