Finding the inverse function of an interpolating function given by NDSolve

Question

Consider the following solution of NDSolve

tf = 100;
sol = NDSolve[{x'[t] == -x[t] + 0.1 y[t] + x[t]^2 y[t], 
    y'[t] == 0.5 - 0.1 y[t] - x[t]^2 y[t], x[0] == 0.5, y[0] == 1.5},
   {x, y}, {t, 0, tf}];
xFunc = x /. First@sol;
Plot[xFunc[t], {t, 0, tf}]

The plot produces

How can I obtain the inverse function of xFunc[t], such that the plot will produce

Mariusz Iwaniuk · Answer 1 · 2018-05-06T13:37:46.377

3

Maybe like so:

tf = 100;
sol = NDSolve[{x'[t] == -x[t] + 0.1 y[t] + x[t]^2 y[t], 
y'[t] == 0.5 - 0.1 y[t] - x[t]^2 y[t], x[0] == 0.5, 
y[0] == 1.5}, {x, y}, {t, 0, tf}];
xFunc = x /. First@sol;
ParametricPlot[{xFunc[t], t}, {t, 0, tf}, AspectRatio -> 1]

Thanks to a good suggestion of user Michael E2

 ParametricPlot[{xFunc[t], -t}, {t, 0, tf}, AspectRatio -> 1, 
 Ticks -> {Automatic, Charting`ScaledTicks[{-# &, -# &}]}]
 Rotate[Plot[xFunc[t], {t, 0, tf}], -90 Degree](*and  My try :P *)

edited May 06 '18 at 13:37

answered May 06 '18 at 07:47

Mariusz Iwaniuk

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I've tried that, but in this manner, ScalingFunctions can not be used in parametric plot, and the plot can not be reversed. – jarhead May 06 '18 at 09:52
@jarhead. What ScalingFunctions do you need? – Mariusz Iwaniuk May 06 '18 at 10:34
It needs to be reversed as In the figure in the question. In any case the inverse function is needed as well. – jarhead May 06 '18 at 11:33
@jarhead The function does not have inverse function (not one-to-one/injective). Please clarify. – Michael E2 May 06 '18 at 11:57
2

ParametricPlot[{xFunc[t], -t}, {t, 0, tf}, AspectRatio -> 1, Ticks -> {Automatic, Charting`ScaledTicks[{-# &, -# &}]}] gives the desired graphics, I think. – Michael E2 May 06 '18 at 11:59

Finding the inverse function of an interpolating function given by NDSolve

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