Function names in feval -Reply

[Gerrit Visser]

>>> "John W. Eaton" <address@hidden> 22/March/2000
11:35am >>>
On 22-Mar-2000, Dirk Laurie <address@hidden> wrote:

| In the following Octave code (2.0.14):
| 
|   function y=integ(f,a,b,n)
|   h=(b-a)/n; x=a+h*(0.5:n);
|   y=h*sum(feval(f,x));
|   endfunction
| 
| the string 'f' may not contain the name of any local variable.
| I.e. if I have coded
| 
|   function y=f(x)
|   y=exp(sin(x));
|   endfunction
| 
| it is illegal to ask for
| 
|   integ('f', 0, 2*pi, 16)

<snip>

How about:

  function y=integ(f,a,b,n)
  h=(b-a)/n; x=a+h*(0.5:n);
  y=h*sum( eval([f, '(x)']) );          % evaluates 'f(x)'
  endfunction

The function is then:

  function y=f(x)
  y=exp(sin(x));
  endfunction

Call integ() then :
octave> integ('f', a, b, n)

or else

octave> integ(('exp(sin(x))', a, b, n))

if integ() is defined as:

  function y=integ(f,a,b,n)
  h=(b-a)/n; x=a+h*(0.5:n);
  y=h*sum( eval(f));          % evaluates 'f'
  endfunction

Hope this helps.

Gerrit



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