Re: Function matrix/vector assembly

[Juan Pablo Carbajal]

On Thu, Aug 9, 2012 at 8:59 AM, Francesco Potortì <address@hidden> wrote:
>>I am trying to assemble a function into a matrix or a vector but I have not
>>found a way to do so except for typing it out manually, which is not
>>possible as the it would be around 100 long and wide and changes after
>>every timestep. The following represents what I am trying to do:
>>
>>f=@(x) [x^2 x 1]
>>then I want to put a number of these into a vector so that the final vector
>>would look like:
>>vect=@(x) [x^2 x+x^2 1+x 1]
>>Here I have added have done something like:
>>vect=@(x) [f(x)(1) f(x)(2)+f(x)(1) f(x)(3)+f(x)(2) +f(x)(3)]
>>So basically having a vector with f in 1 to 3 added to f in positions 2 to
>>4. Obviously this would have to run in a loop as it is well over 100 wide.
>
> As far as I am concerned, you should try to explain it better: I read it
> carefully, but could nt make out what you need.
>
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I am not sure I understood.
What I get is the following: you want to define vector-valued
functions and then be able to operate on those functions (add them,
multiply them, etc).

I do not think there is built in operator for anonymous handles, that is [1]
f  = @(x) x.^2
g = @(x) x
h = f + g

and h should be the anonymous function accepting two input argument such that
h(x,y) = f(x) + g(y)

To emulate this, afaik you have to do it manually (and it wouldn't be efficient)
h = @(x,y) f(x) + g(y)

Now when you call h, you will be then calling f and g, and since
function evaluations are not the most efficient thing, this get worse
themore function you nest.

@John | Jordi: Can [1], i.e. operators between anonymous functions, be
implemented efficiently?
-- 
M. Sc. Juan Pablo Carbajal
-----
PhD Student
University of Zürich
http://ailab.ifi.uzh.ch/carbajal/