Getting only first component from vector/matrix output

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Positronized
Positronized 2011년 4월 1일
I'm using ode45 to solve a second-order IVP and want to use deval to evaluate the solution.
Since the equation was second-order, the solution vector has two components. I am wondering if there's an easy way to just get only the first component without having to assign deval's output to a temporary variable first?
I would've expected syntax like (deval(sol,x))(1) to work but it doesn't.
The same question applies not just to deval, but to any function which returns a vector/matrix.

채택된 답변

Walter Roberson
Walter Roberson 2011년 4월 1일
subsref(deval(sol,x),struct('type','()','subs',1))
If you are doing this multiple times, then just use (e.g.,)
first = @(x) x(1);
first(deval(sol,x))

추가 답변 (1개)

Sean de Wolski
Sean de Wolski 2011년 4월 1일
No. MATLAB does not support cascading indexing (except for in structures; which wouldn't be applicable here).
  댓글 수: 3
Sean de Wolski
Sean de Wolski 2011년 4월 1일
You can use Walter's function handle, that will do it in one line. The temporary variable will still have to be created; however, in addition to the creation of the function handle and the call to it. What's so bad about having to return a temp variable?
Positronized
Positronized 2011년 4월 1일
Nothing in general, it's just that I was trying to hack together a quick 1-line function handle without creating an M-file. I'll accept Walter's answer.

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