# Avoid error when using piecewise function in NDSolve?

Posted 7 months ago
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 I am trying to use piecewise function in NDSolve but get error message that follows: Any idea why? I tried the residue method as specified in warning, but did not get results that make sense. Help is greatly appreciated!!! Attachments:
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Posted 7 months ago
 HiYour M[r] function is constantly growing, so it does not have a maximum.Regards, MI. Attachments:
 With a few PiecewiseExpand it gives a solution: Pf[r_, \[Rho]_] := Piecewise[{{K*(\[Rho][r])^( 5/3), \[Rho][ r] < \[Rho]low}, {(\[Rho]high*c^2 - K*\[Rho]low^(5/3))/(\[Rho]high - \[Rho]low)*\[Rho][ r], \[Rho]low <= \[Rho][r] <= \[Rho]high}, {\[Rho][r]* c^2, \[Rho][r] > \[Rho]high}}]; MassEqf = (M'[r] == 4 \[Pi] *\[Rho][r]* r^2); PressureEqf = (\[Rho]'[r] PiecewiseExpand[ D[Pf[r, \[Rho]], r]/\[Rho]'[r]] == PiecewiseExpand[-(( G*(M[r] + 4 \[Pi]*r^3*Pf[r, \[Rho]]/c^2)*(\[Rho][r] + Pf[r, \[Rho]]/c^2))/(r^2*(1 - 2*G*M[r]/(r*c^2))))]);