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Student Support Forum: 'Invalid integration variable or limit(s)' topicStudent Support Forum > General > Archives > "Invalid integration variable or limit(s)"

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John
08/31/05 10:14pm

Hello,
I get the following error message when I include the conditional into my definition for function f[a_}: Invalid integration variable or limit(s). Without this conditonal statement,
x[1] equals a negative number, which is not realistic. The smallest number x[t] can equal is 0. I believe the error message is because
x[t] takes on a constant numerical value due to the conditional statement and it forms the
d(x[t]) part of the integral. Do you have any suggestions to get around this? If x[t]<=0.0001, I would like x'[t]=0 and y'[t]=-2*a*y[t].

Here are my equations:

f[a_]:=NDSolve[{x'[t]==If[x[t]<=0.0001,0,-1.86*
(1-y[t])*Integrate[x[t]^(2/3),{x[t],0,1}],
y'[t]==If[x[t]<=0.0001,-2*a*y[t],-x'[t]-2*a*y[t],
x[0]==1,y[0]==0},{x,y},{t,0,1},
Method->StiffnessSwitching]

f[10]

Thank you


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Subject (listing for 'Invalid integration variable or limit(s)')
Author Date Posted
Invalid integration variable or limit(s) John 08/31/05 10:14pm
Re: Invalid integration variable or limit(s) yehuda ben-s... 09/01/05 06:37am
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