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Confusion, matlab, ode45 variables.

  1. Apr 22, 2011 #1
    1. The problem statement, all variables and given/known data

    I am very confused over how matlab knows which variables are changeable variables in ode45.

    2. Relevant equations // 3. The attempt at a solution

    My input is p

    Earlier have defined;
    a = 1;
    k = 1;
    w = 1/3;

    Then I want to figure out adot and adoubledot from these.

    adot = (a)*(p - k/a)^(-1/2);

    adoubledot = (a/2)*(p + 3*w*p);

    Suddenly realised that I have no idea why matlab would let "a" change but not let "p" and "k" change...

    Is there a way to tell matlab that one of the variables is changing in time and the others aren't?
  2. jcsd
  3. Apr 23, 2011 #2
    Nobody? =( Does my question make sense?
  4. Apr 23, 2011 #3


    User Avatar
    Gold Member

    I'm not sure exactly what you're asking. For ode45 you need to define a function. Ode45 uses the function definition for variables. (I think you need to have only one variable For ode45, so if you have more than one you can use a column vector.)
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