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I have:

f[x_, y_] = 1 - y;
g[x_, y_] = x^2 - y^2;
sol[{x0_, y_ 0}] := 
 NDSolveValue[{x'[t] == f[x[t], y[t]], y'[t] == g[x[t], y[t]], 
   x[0] == x0, y[0] == y0}, {x[t], y[t]}, {t, 0, 15}]

Then:

sol[{2, 1}]

Which returns:

{InterpolatingFunction[{{0., 15.}}, <>][t], 
 InterpolatingFunction[{{0., 15.}}, <>][t]}

But when I try:

toplot = Map[sol, {{2, 1}}]

It returns:

enter image description here

Notice that there is no comma this time between the first and second interpolating function. Why not?

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  • 1
    $\begingroup$ There is a comma if I do as you input. However, it seems that you asked for MatrixForm, and the matrix form of a list does not have comma in between elements. $\endgroup$
    – Yi Wang
    Commented Apr 16, 2015 at 0:59
  • $\begingroup$ That is correct. Thanks. $\endgroup$
    – David
    Commented Apr 16, 2015 at 3:25

1 Answer 1

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After correcting the typo in the argument to sol ({x0_, y_ 0} to {x0_, y0_}), I cannot reproduce your problem:

$Version

"10.1.0 for Mac OS X x86 (64-bit) (March 24, 2015)"

f[x_, y_] = 1 - y;
g[x_, y_] = x^2 - y^2;
sol[{x0_, y0_}] := 
 NDSolveValue[{x'[t] == f[x[t], y[t]], y'[t] == g[x[t], y[t]], x[0] == x0, 
   y[0] == y0}, {x[t], y[t]}, {t, 0, 15}]

toplot = Map[sol, {{2, 1}}]

enter image description here

 Plot[toplot, {t, 0, 15}, PlotRange -> All]

enter image description here

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1
  • $\begingroup$ Thanks for the notice. I've discovered it myself this morning. $\endgroup$
    – David
    Commented Apr 16, 2015 at 16:46

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