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From: Antonio Garcia-Martinez on 23 Feb 2010 20:29
firt I built a Matrix of syms with the instruction "jacobian" of matlab,


syms XI XM XT XV

dXIdt = -RI + EPS*RP*XI + (WI/XV) - (QE/XV)*XI;
dXMdt = -RP + EPS*RP*XM + (QE/XV)*(XME - XM);
dXTdt = BET*RM - GAM*(XT - TC) + (QE/XV)*(TE - XT)*(1 - EPS*XME)/(1 - ...
EPS*XM);
dXVdt = -EPS*RP*XV + QE - Q;
dXdt = [dXIdt, dXMdt,dXTdt,dXVdt];

xE=[XI,XM,XT,XV];

dAm=jacobian(dXdt,xE);

then I try to eval the matrix defining the syms vars

XI= 0.002001;XM = 0.993302;XT = 314.6209;XV=2000;Q = 39.9075;

I've been using the instruction "eval" to eval a Matrix in Matlab 2007 and 2008 and it works

Axx=eval(dAm);


but when I tried to use it in Matlab 2009 send the error :

??? Error using ==> evalin
Undefined function or variable 'PI'.

Error in ==> sym.eval at 15
s = evalin('caller',vectorize(map2mat(char(x))));

So I need help for to fix this problem
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