Re: error with function handles

[simone marras]

Perfect! It works now; i was indeed using an old saved copy of one of the files!
thank you very much for the help!

Best,
s


On Wed, Aug 19, 2009 at 3:10 PM, Martin Helm<address@hidden> wrote:
> Am Mittwoch, 19. August 2009 14:50:34 schrieb simone marras:
>> Hi everyone, thanks for helping.
>>
>> I corrected the errors that you pointed out but still obtained exactly
>> the same error that I would get initially. To summarize the steps,
>> this is what we have:
>>
>> 1)
>>
>> >> function y = fun(x)
>> >>
>>  >   y = 10*exp(-50.0*abs(x));
>> >
>> >    endfunction
>>
>> 2)
>>
>> function int = midpntc(a, b, m, fun)
>>
>>       h=(b-a)/m
>>       x=[a+h/2:h:b];
>>
>>       k = max(size(x));
>>
>>       y = fun(x);
>>
>>       if size(y) == 1, y = diag(ones(k))*y; end
>>
>>       int = h*sum(y);
>> end
>>
>> 3) And finally, call to midpntc as:
>>
>> octave:72> midpntc(0, 1,10, @fun)
>> h =  0.10000
>> error: octave_base_value::convert_to_str_internal (): wrong type
>> argument `function handle'
>> error: eval: expecting std::string argument
>> error: evaluating assignment expression near line 13, column 4
>> error: called from `midpntc' in file
>> `/home/simone/Documents/scientific/CFD/myCFD_library/ATMOSPHERE_miscellanea
>>/TMP/midpntc.m'
>>
>>
>> I am lost
>> S.
>>
>> On Wed, Aug 19, 2009 at 2:45 PM, Martin Helm<address@hidden> wrote:
>> > Am Mittwoch, 19. August 2009 14:18:30 schrieb simone marras:
>> >> Hi,
>> >>
>> >> I am trying to call a function that accepts a function handle as
>> >> argument. My functions are all defined within the same directory where
>> >> myfun.m rerturns a simple expression as:
>> >>
>> >> function y = myfun(x)
>> >>      y = 10*exp(-50.0*abs(x)) - 0.01/((x-0.5).*(x-0.5) + 0.001) +
>> >> 5.0*sin(5.0*x);
>> >> endfunction
>> >>
>> >> and midpntc is defined as:
>> >>
>> >> function [Int] = midpntc(a, b, m, function)
>> >>
>> >>     h=(b-a)/m
>> >>       x=[a+h/2:h:b];
>> >>
>> >>       k = max(size(x));
>> >>       y = eval(fun);
>> >>
>> >>       if size(y) == 1, y = diag(ones(k))*y; end
>> >>
>> >>       int = h*sum(y);
>> >>
>> >> when I call midpntc in octave as:
>> >> >> Int = midpntc(0, 1, 10, "myfun")
>> >>
>> >> I obtain the following error:
>> >>
>> >>  midpntc(0,1,10,"myfun")
>> >> h =  0.10000
>> >> error: `x' undefined near line 2 column 9
>> >> error: evaluating binary operator `.^' near line 2, column 10
>> >> error: evaluating binary operator `-' near line 2, column 13
>> >> error: evaluating binary operator `-' near line 2, column 17
>> >> error: evaluating binary operator `./' near line 2, column 6
>> >> error: evaluating assignment expression near line 2, column 3
>> >> error: called from `myfun'
>> >> error: evaluating assignment expression near line 13, column 4
>> >> error: called from `midpntc' in file
>> >> `/home/simone/Documents/scientific/CFD/myCFD_library/ATMOSPHERE_miscella
>> >>nea /TMP/midpntc.m'
>> >>
>> >>
>> >> while, if I use the syntax
>> >>
>> >> >> Int = midpntc(0, 1, 10, @myfun)
>> >>
>> >> the error that I get is:
>> >>
>> >> h =  0.10000
>> >> error: octave_base_value::convert_to_str_internal (): wrong type
>> >> argument `function handle'
>> >> error: eval: expecting std::string argument
>> >> error: evaluating assignment expression near line 13, column 4
>> >> error: called from `midpntc' in file
>> >> `/home/simone/Documents/scientific/CFD/myCFD_library/ATMOSPHERE_miscella
>> >>nea /TMP/midpntc.m'
>> >>
>> >>
>> >> Could anyone help me with this issue?
>> >> Thank you very much in advance,
>> >>
>> >> S.
>> >
>> > Hello,
>> >
>> > if you really want to pass the function name as string you should use
>> > feval instead of eval to evaluate it.
>> >
>> > y = feval(fun, x);
>> >
>> > Or you simply use a function handle instead of a string
>> >
>> > midpntc(0,1,10,@myfun)
>> >
>> > and in midpntc
>> >
>> > y = fun(x);
>> >
>> > instead of eval
>> >
>> > Hope that helps.
>> >
>> > - mh
>
>
> From your error message I can see that your function still uses eval
>
>> error: octave_base_value::convert_to_str_internal (): wrong type
>
> So it seems your updated version of midptnc did not come into effect.
> Try
> clear midpntc
> to delete the old function definition which seems to persist in your RAM.
>
> - mh
>
>



-- 
Simone Marras, Ph.D. candidate
Barcelona Supercomputing Center
Universitat Politecnica de Catalunya
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