/* Sets nseg in each section to an odd value so that its segments are no longer than d_lambda x the AC length constant at frequency freq in that section. Be sure to specify your own Ra and cm before calling geom_nseg() To understand why this works, and the advantages of using an odd value for nseg, see Hines, M.L. and Carnevale, N.T. NEURON: a tool for neuroscientists. The Neuroscientist 7:123-135, 2001. */ // these are reasonable values for most models // freq = 100 // Hz, frequency at which AC length constant will be computed // d_lambda = 0.1 func lambda_f() { local i, x1, x2, d1, d2, lam if (n3d() < 2) { return 1e5 * sqrt(diam / (4 * PI * \$1 * Ra * cm)) } // above was too inaccurate with large variation in 3d diameter // so now we use all 3-d points to get a better approximate lambda x1 = arc3d(0) d1 = diam3d(0) lam = 0 for i = 1, n3d() - 1 { x2 = arc3d(i) d2 = diam3d(i) lam += (x2 - x1)/sqrt(d1 + d2) x1 = x2 d1 = d2 } // length of the section in units of lambda lam *= sqrt(2) * 1e-5 * sqrt(4 * PI * \$1 * Ra * cm) return L / lam } proc geom_nseg() { local freq, d_lambda freq = \$1 d_lambda = \$2 forall { nseg = int((L / (d_lambda * lambda_f(freq)) + 0.9) / 2) * 2 + 1 } }