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Assign values to an NDSolve inside a For loop

Posted 4 months ago
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Hello, I am trying to assign the values of Solve function to an NDSolve inside a For loop. To be more precise: I use Solve to find the values of p as shown in the example and then, I would like to use each value of p to compute the NDSolve function. These are test functions because the originals are too big to post them. The idea remains the same though. The integration seems to stop at step one. Below is what i am trying to do. I have uploaded the script too.

Thank you all in advance

For[i = 1, i < 4, i = i + 1, 
t = p /. Solve[p - 2 i == 0]; 
 s = NDSolve[{y'[x] == t*y[x] Cos[x + y[x]], y[0] == 1},    y, {x, 0, 30}];
 Print@Plot[Evaluate[y[x] /. s], {x, 0, 30}, PlotRange -> All];]
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2 Replies

Hello Agapi Pop,

to make your code run you need to rewrite the second line like so:

t = First[p /. Solve[p - 2 i == 0]];

This is, because here the result of Solve is a List containing one element, and you want that element only.

But - if I may add - a more Mathematica like coding would read:

t = Flatten@Table[p /. Solve[p - 2 i == 0, p], {i, 1, 4}];
s = NDSolveValue[{y'[x] == #*y[x] Cos[x + y[x]], y[0] == 1}, y, {x, 0, 30}] & /@ t;
Plot[Evaluate@Through[s[x]], {x, 0, 30}, PlotRange -> All]
(* or likewise: *)
Plot[#[x], {x, 0, 30}, PlotRange -> All] & /@ s

enter image description here

Posted 4 months ago

I cannot thank you enough. Your coding proposal is so elegant. Thank you again!

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