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 Author Comment/Response Francesco 03/02/13 1:16pm Dear All, I am having some problems trying to use the solution to NDsolve in the Piecewise function. I am solving the following system of coupled ODEs (it looks horrible but it works): s = NDSolve[{x'[z] == 0.3513*(T[z]*10^(-4))^(-0.6166)/(1 + 0.6703*(T[z]*10^(-4))^(0.53))*(1 +z)^(-2.5)*(0.206*(1 + z)^3*x[z]^2 - 2.415*10^(21)*T[z]^(1.5)*Exp[-1.578*10^5/T[z]] (1 - x[z]))/(1 + 8*10^7*(10^(-4)*T[z])^(0.7)*Exp[-3.95*10^4/T[z]]) - 7.7* Exp[-(1.195/8.5)^2*(1 + z)^2]*(1 - x[z]), (1 + z)*T'[z] == 2*T[z] - 0.022*(1 + z)^(2.5)*x[z] /(1.08 + x[z])*(2.728*(1 + z) - T[z]) - 5.23*10^6*0.1*(1 - (1 - x[z]^0.2663)^1.3163)*(1 + z)*1.348/8.5* Exp[-(1.195/8.5)^2*(1 + z)^2], T[1800] == 4914, x[1800] == 1}, {T, x} , {z, 7, 1800}] As the system fails to integrate at small z, but I know x must equal 1, I am the trying to define: xx[z_] := Piecewise[{{1, z < 10}, {x[z] /. s, z > 10}}] Plot[xx[z], {z, 0, 30}] But it does not plot anything... Any suggestions URL: ,

 Subject (listing for 'NDsolve and Piecewise') Author Date Posted NDsolve and Piecewise Francesco 03/02/13 1:16pm Re: NDsolve and Piecewise yehuda 03/02/13 5:19pm Re: NDsolve and Piecewise Bill Simpson 03/02/13 8:38pm Re: NDsolve and Piecewise Peter Pein 03/03/13 02:23am
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