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I try to draw a graph:


     ClearAll[k, r, n]
    k = 20
    r = .8

    Manipulate[
     psol = DSolve[{p'[t] == r*p[t] (1 - p[t]/k), p[0] == n}, p[t], t];
     Plot[ psol[t] , {t, -10, 10} ], {n, 0, 1}]

but I get an error:

Inverse functions are being used by Solve, so some solutions may not be found; use Reduce for complete solution information.

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1 Answer 1

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The message is warning that inverse functions are being used by Solve, so some solutions may not be found

You can ignore it if you want

ClearAll[k, r, n]
k = 20
r = .8
Manipulate[
 psol=Quiet[DSolve[{p'[t]==r*p[t] (1-p[t]/k),p[0]==n},p[t],t]];
 Plot[p[t]/.psol,{t,-10,10}],
 {{n,0,"n"},0,1,Appearance->"Labeled"}
]

Or it might be better to turn off that one messaage

Manipulate[
  psol=DSolve[{p'[t]==r*p[t] (1-p[t]/k),p[0]==n},p[t],t];
  Plot[p[t]/.psol,{t,-10,10}],{{n,0,"n"},0,1,Appearance->"Labeled"}
,Initialization:>
{
  k=20;
  r=.8;
  Off[Solve::ifun]
}
]

enter image description here

see ref/message/Solve/ifun for more information on this message

Mathematica graphics

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3
  • $\begingroup$ You can still use Quiet[] to turn off a single message locally: Quiet[Solve[y == x Exp[x], x], Solve::ifun]. $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Nov 5, 2017 at 20:57
  • $\begingroup$ If plotting the solution is the only goal, you could just use NDSolve. $\endgroup$
    – aardvark2012
    Commented Nov 6, 2017 at 10:22
  • $\begingroup$ Rather than repeatedly evaluating DSolve, move that to the Initialization: Manipulate[ Plot[sol[n, t], {t, -10, 10}, PlotRange -> {0, 20}], {{n, 0}, 0, 1, 0.01, Appearance -> "Labeled"}, Initialization :> {k = 20; r = 4/5; sol[n_, t_] = p[t] /. DSolve[{p'[t] == r*p[t] (1 - p[t]/k), p[0] == n}, p, t][[1]] // Quiet}] $\endgroup$
    – Bob Hanlon
    Commented Dec 5, 2017 at 20:11

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