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(MATLAB) Ignoring output arguments

  1. Jul 6, 2006 #1
    Hey all,

    Suppose I have a MATLAB function that returns two (or more) output arguments, but I only care about the second one, and I do not wish to assign the value of the first one to a variable.

    What bugs me is when, for example, I solve an ODE:

    [t, x] = ode45(blablabla)

    and then MATLAB editor's automatic syntax checker tells me that the variable 't' is never used. Of course it isn't, because I don't need it :P But more importantly, it uses some memory unnessarily. So, is there any way to totally ignore that argument?

    Thank you all!
     
  2. jcsd
  3. Jul 6, 2006 #2

    shmoe

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    I haven't used matlab in ages, but if a function returns a vector is it not possible to pick off one component like:

    x=ode45(blablabla)[2]
     
  4. Jun 30, 2010 #3
    I have been wondering exactly the same thing. Haven't found a answer, though.

    Just to be clear, it is not about selecting a value of a returned vector, but selecting a specific output. It is especially annoying if I have a multiple output arguments.

    function [A,B,C,D,E,F] = myFun(inputarg)
    ...​
    end

    If I only want the last output argument F I usually just do the following
    [dummy, dummy, dummy, dummy, dummy, F] = myFun(input)

    but its ugly.
     
  5. Jun 30, 2010 #4
    edit the code or save as the original function without the extra arguments if it is really important to you.
     
  6. Jun 30, 2010 #5
    Newer versions of Matlab let you use a ~ in place of the output variables you choose to ignore. So instead of

    [dummy, dummy, dummy, dummy, dummy, F] = myFun(input),

    you could put

    [~, ~, ~, ~, ~, F] = myFun(input)

    See this blog post for more info.
     
  7. Jul 1, 2010 #6
    Wow, that is handy. Thanks for the link.
     
  8. Jul 21, 2012 #7
    Simply change the position of the variables
    [x, t] = ode45(blablabla)
     
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