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Mathematics Equation Solving Wolfram Language

Why does NDSolve return input with no error?

Christopher Kribs

Christopher Kribs, University of Texas at Arlington

Posted 4 years ago

When I run the following NDSolve command, Mathematica 12.0 just spits back my input as its output, with no error messages. Why is it failing to execute? I have been all over the syntax, but can find nothing wrong. NDSolve[{S'[t]==-10,EE'[t]==-10,I0'[t]==2-0.167122 I0[t], I1'[t]==2-0.0714286 I1[t],I2'[t]==2-0.1 I2[t],I3'[t]==2-0.1 I3[t], I4'[t]==2-0.0892857 I4[t],RR'[t]==0.167122 I0[t]+0.0714286 I1[t]+0.1 I2[t]+0.1 I3[t], S[0]==399753.,EE[0]==1000,I0[0]==230.799, I1[0]==11.4638,I2[0]==1.92257,I3[0]==1.28089, I4[0]==1.33272,RR[0]==0},{S[t],EE[t],I0[t],I1[t],I2[t],I3[t],I4[t],RR[t]},{t,0,180}]

When I run the following NDSolve command, Mathematica 12.0 just spits back my input as its output, with no error messages. Why is it failing to execute? I have been all over the syntax, but can find nothing wrong.

    NDSolve[{S'[t]==-10,EE'[t]==-10,I0'[t]==2-0.167122 I0[t],
I1'[t]==2-0.0714286 I1[t],I2'[t]==2-0.1 I2[t],I3'[t]==2-0.1 I3[t],
I4'[t]==2-0.0892857 I4[t],RR'[t]==0.167122 I0[t]+0.0714286 I1[t]+0.1 I2[t]+0.1 I3[t],
 S[0]==399753.,EE[0]==1000,I0[0]==230.799,
I1[0]==11.4638,I2[0]==1.92257,I3[0]==1.28089,
I4[0]==1.33272,RR[0]==0},{S[t],EE[t],I0[t],I1[t],I2[t],I3[t],I4[t],RR[t]},{t,0,180}]

POSTED BY: Christopher Kribs

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Bill Nelson

Posted 4 years ago

Your latest screenshot looks like it has curly braces on the right side of IO'[t]=={...} and on the right side of RR'[t]=={...} and those really worry me. I do not see those curly braces in the code that you pasted in your first post. Curly braces in Mathematica define lists and are completely different from parens. Let's try a quick experiment. Scrape your code from your first post into your clipboard. Open a second fresh empty browser window. Go to https://www.wolframcloud.com/objects/b3m2a1/LetMeMathematicaThatForYou.html Patiently wait for that to initialize until you see the "Type your..." appear. Below that in the large white empty space give it one left mouse click and wait a few seconds for it to initialize Paste your code. Patiently wait, perhaps half a minute for that to appear. <shift>+<enter> Patiently wait, perhaps half a minute for something to appear. Do you see eight interpolating functions?

POSTED BY: Bill Nelson

Shenghui Yang

Shenghui Yang, WOLFRAM

Posted 4 years ago

Same as Nelson, copy and paste the code into a notebook just works.

POSTED BY: Shenghui Yang

Bill Nelson

Posted 4 years ago

It works for me with no changes. Have you tried turning the computer off and back on again? Really. If that does make it work then that may mean that you previously assigned some value to some symbol and didn't realize that Mathematica was remembering that assignment.