vpasolve returns empty structure while fimplicit nicely plots

Christian Bauer

2018 11 28

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3 次查看（30 天）

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Hi,

I have the following problem. I have two moderately nasty equations of two variables theta and nu, which I can plot nicely uusing fimplicit. There are two intersections, one in the middle (close to the parameter xss = theta) and one at nu=0. I'm interested in the first one, however solve or vpasolve return only a struct object with no values inside. How can I solve this? I need an approximate numerical solution, so I can automize it to get this equilibria for a grid of xss, ses and sds parameter values.

Best,

Christian

ses=0.05;

sds=0.05;

xss=0.2;

dc=1;

interv=[-0.1 0.4 0 0.7]

dummy= @(theta,nu) pdf('Normal',(-theta+cdf('Normal',(xss-theta-nu)/ses,0,1))/sds,0,1) * pdf('Normal',(xss-theta-nu)/ses,0,1)/(ses*sds) - dc

dummy2= @(theta,nu) dc*nu+pdf('Normal',(-theta+cdf('Normal',(xss-theta-nu)/ses,0,1))/sds,0,1) - pdf('Normal',(-theta+cdf('Normal',(xss-theta)/ses,0,1))/sds,0,1)

fimplicit(dummy,interv)% die obere kurve ist das MIN!!!

hold on

fimplicit(@(theta,nu) xss-theta-nu,interv)

fimplicit(dummy2,interv)

hold off

syms dvarthet dvarnu

eqns = [dummy(dvarthet, dvarnu)==0,dummy2(dvarthet, dvarnu)==0]

vpasolvevpasolve(eqns,[dvarthet dvarnu])