# Obtain transfer function from signal flow graph

I have a pretty complex signal flow graph with all the blocks and the branches completely describing an analog filter, in the Laplace complex variable s. The signal $X(s)$ is the input and $Y(s)$ is the output.

Is there any (free) tool which can analyze such a graph and provide the overall transfer function $H(s) = Y(s)/X(s)$?

Googling I found this Matlab tool, but the tool it is not free; anyway is there anything similar, in Matlab or in other environments?