My Euler Method Error

Question

Bob 2015-10-7

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/247346-my-euler-method-error

编辑： Bob 2015-10-13

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Question:

Consider the initial value problem: dy/dt= e−t − 3y, y(−1) = 0.

Part a: Use the MATLAB program myeuler.m from Chapter 8 to compute the Euler Method approximation to y(t) with step size h = 0.5 and n = 4 steps. The program will generate a list of ordered pairs (ti, yi). Use plot to graph the piecewise linear function connecting the points (ti, yi). Repeat with h = 0.2 and n = 10.

Code:

f = @(t,y) exp(-t)-3*y;
[t, y] = myeuler(f,-1,0,1,4);
plot(t,y)
[t, y] = myeuler(f,-1,0,1,10)
plot(t,y)

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Bob 2015-10-13

I keep getting an error:

Error in Project_2 (line 94) [t, y] = myeuler(f,-1,0,1,4);

Bob 2015-10-13

Need help with this asap!

Thanks

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Answer 1

Walter Roberson 2015-10-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/247346-my-euler-method-error#answer_195775

Your code executes without error when I try it without change.

Make sure that the code you posted for myeuler is saved in myeuler.m and that the directory it is saved in is on your MATLAB path (for example if you are cd'd to the same directory)

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Walter Roberson 2015-10-13

在 MATLAB Online 中打开

>> f = @(t,y) exp(-t)-3*y;
[t, y] = myeuler(f,-1,0,1,4);
plot(t,y)
[t, y] = myeuler(f,-1,0,1,10)
plot(t,y)
t =
                          -1
                        -0.8
                        -0.6
                        -0.4
                        -0.2
       -5.55111512312578e-17
                         0.2
                         0.4
                         0.6
                         0.8
                           1
y =
                           0
           0.543656365691809
           0.662570731975217
           0.629452052868189
            0.55014576067553
           0.464338855902246
           0.385735542360898
           0.318040367559956
            0.26128015623111
           0.214274389711249
           0.175575548707944
>> dbtype myeuler.m
1       function [t, y] = myeuler(f, tinit, yinit, b, n)
2       
3       %MYEULER Euler approximation for initial value problem,
4       
5       % dy/dt = f(t, y), y(tinit) = yinit.
6       
7       % Approximations y(1),..., y(n + 1) are calculated at
8       
9       % the n + 1 points t(1),..., t(n + 1) in the interval
10      
11      % [tinit, b]. The right-hand side of the differential
12      
13      % equation is defined as an anonymous function f.
14      
15      % Calculation of h from tinit, b, and n.
16      
17      h = (b - tinit)/n;
18      
19      % Initialize t and y as length n + 1 column vectors.
20      
21      t = zeros(n + 1, 1);
22      
23      y = zeros(n + 1, 1);
24      
25      % Calculation of points t(i) and the corresponding
26      
27      % approximate values y(i) from the Euler Method formula.
28      
29      t(1) = tinit;
30      
31      y(1) = yinit;
32      
33      for i = 1:n
34      
35      t(i + 1) = t(i) + h;
36      
37      y(i + 1) = y(i) + h*f(t(i), y(i));
38      
39      end

Bob 2015-10-13

编辑：Bob 2015-10-13

Now I am getting this:

Maximum recursion limit of 500 reached. Use set(0,'RecursionLimit',N) to change the limit. Be aware that exceeding your available stack space can crash MATLAB and/or your computer.

Bob 2015-10-13

编辑：Bob 2015-10-13

What is which -all myeuler? Should I have that somewhere in the code?

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My Euler Method Error

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