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nirupama radhakrishnan

there seems to be a problem with derivative

nirupama radhakrishnan, NIT TRICHY

Posted 9 years ago

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NDSolve[{Derivative[1][x][t] == 0.5[x[t]][1 + x[t]][2 - x[t]] y[t], Derivative[1][y][t] == -y[t]^2 - 1.5 x[t] y[t]^2, x[0] == 4, y[0] == 10000}, {x, y}, {t, 1000}] this is not getting solved as it says non numerical derivative found at t==0. Can anyone help me in this regard?

POSTED BY: nirupama radhakrishnan

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Marco Thiel

Marco Thiel, University of Aberdeen - Dept. of Physics/Mathematics

Posted 9 years ago

See also: http://community.wolfram.com/groups/-/m/t/283458?ppauth=JmC8Wl27 (repeated posting)

POSTED BY: Marco Thiel

Bill Simpson

Posted 9 years ago

You have used [ and ] instead of ( and ) and those have completely different meanings to Mathematica. In[2]:= NDSolve[{x'[t] == 0.5 (x[t]) (1 + x[t]) (2 - x[t]) y[t], y'[t] == -y[t]^2 - 1.5 x[t] y[t]^2, x[0] == 4, y[0] == 10000}, {x, y}, {t, 1000}] Out[2]= {{x ->InterpolatingFunction[{{0.`,1000.`}},<>], y -> InterpolatingFunction[{{0.`,1000.`}},<>]}}

You have used [ and ] instead of ( and ) and those have completely different meanings to Mathematica.

In[2]:= NDSolve[{x'[t] == 0.5 (x[t]) (1 + x[t]) (2 - x[t]) y[t], 
  y'[t] == -y[t]^2 - 1.5 x[t] y[t]^2, x[0] == 4, y[0] == 10000}, {x, y}, {t, 1000}]

Out[2]= {{x ->InterpolatingFunction[{{0.`,1000.`}},<>],
y -> InterpolatingFunction[{{0.`,1000.`}},<>]}}

POSTED BY: Bill Simpson

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