2 matplotlib.use('Agg') # select backend that doesn't require X Windows
10 def zr(a,b,p,q) : # p, q \in {-1,1}
11 return p*i*b/2.0 * (1 + q*sqrt(complex(1,0) - (2*a/b)**2))
12 def zrc(c,b,p,q) : # p, q \in {-1,1}
13 return p*i*b/2.0 * (1 + q*sqrt(complex(1,0) - (2*c)**2))
22 plot(dpp.real,dpp.imag,'ro', label="++")
23 plot(dmp.real,dmp.imag,'b+', label="-+")
24 plot(dpm.real,dpm.imag,'gx', label="+-")
25 plot(dmm.real,dmm.imag,'k.', label="--")
27 legend(loc='upper right')
29 plot(c, dpp.real,'ro',
35 plot(c, dpp.imag,'ro',
43 # critically damped for b^2 = 4a^2
44 # so for c = a/b = 0.5
45 #for b in [0.1, 1, 2, 4, 6] :
50 FIGURE.savefig("figure.png")