Re: Unable to obtain value from interpolation function integration
- To: mathgroup at smc.vnet.net
- Subject: [mg59601] Re: Unable to obtain value from interpolation function integration
- From: "antononcube" <antononcube at gmail.com>
- Date: Sat, 13 Aug 2005 03:26:37 -0400 (EDT)
- References: <ddhjqj$h7q$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Using Mathematica code based on the formulas in your post, everything
works fine. Please, provide the exact Mathematica code you have used.
(Also, it will be better if there are no special symbols in it, in
order to be easier to copy and paste it.)
In[4]:= lambdar = 7.31^-10;
lambdad = 5.63^-8 ;
lambdas = 5^-7.;
In[8]:=f[t_] := f[t_] := (0.0022 + 0.0086/(1 + t/3600) + 1.89^-7*t -
7.60^-12*t^2 + 1.72^-16*t^3 - 1.77^-21 t^4 + 6.27^-27*t^5)
In[9]:= solution =
NDSolve[
{y1'[t] == -( lambdar + lambdad)*y1[t] +
lambdas*y2[t] + (1 - UnitStep[t - 86400]*4.04^17*f[t]),
y2'[t] == lambdad*y1[t] - lambdas*y2[t],
y1[0] == 0,
y2[0] == 0},
{y1[t], y2[t]}, {t, 0, 100000.}]
NDSolve::ndsz: At t == 86400., step size is effectively zero;
singularity or
stiff system suspected.
Out[9]= {{y1[t] -> InterpolatingFunction[{{0., 86400.}}, <>][t],
y2[t] -> InterpolatingFunction[{{0., 86400.}}, <>][t]}}
In[10]:= (y1[t] /. solution)[[1]]
Out[10]= InterpolatingFunction[{{0., 86400.}}, <>][t]
In[11]:= NIntegrate[(y1[t] /. solution)[[1]], {t, 90000, 91800}]
Out[11]=1.8598667775520015*^24
Anton Antonov,
Wolfram Research, Inc.