Does anybody know what the exact meaning of the following command?
3 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Does anybody know what the exact meaning of the following command?
D = @(x,y)f(x,y).*(g(x ,y)>0);
If it possible, answer by an example.
0 commentaires
Réponse acceptée
Matt J
le 6 Déc 2023
Modifié(e) : Matt J
le 6 Déc 2023
It defines an anonymous function of x,y. Everything after @(x,y) is the expression that will be evaluated. E.g.,
D=@(x,y) x+y;
D(1,0)
D(1,2)
D(10,13)
5 commentaires
Walter Roberson
le 6 Déc 2023
Combining:
D = @(x,y)f(x,y).*(g(x ,y)>0);
evaluates to:
- f(x,y) in locations where g(x,y) is > 0
- NaN in locations where f(x,y) is -inf or +inf and g(x,y) <= 0
- 0 in locations where f(x,y) is finite and g(x,y) <= 0
Most people forget about the inf -> nan problem: most people would summarize D as being 0 where g(x,y)<=0 and f(x,y) where g(x,y)>0 -- but that is wrong for the case of infinite f(x,y)
Matt J
le 6 Déc 2023
Modifié(e) : Matt J
le 6 Déc 2023
can we say that D defines f only within the domain of g>0 (limits f to the domain of g>0)?
No, D is defined for all (x,y), in the sense that any (x,y) pair you give it as input will return a result. The g>0 part is simply to ensure that D=0 whenever g<=0 (assuming f(x,y) is finite for all x,y). Here is a 1D example that may make this clearer:
t=linspace(-1,1,25);
D=@(x) 2*(x>0);
plot(t,D(t),'--x'); axis padded %plot of a step fucntion
As you can see, D(t) returns plottable values for both positive and negative t. It is simply that D(t)=0 for negative t.
Plus de réponses (0)
Voir également
Catégories
En savoir plus sur Logical dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!