Question on summing function handles

6 次查看（过去 30 天）
Jordan Boote
Jordan Boote 2022-3-24
编辑： VBBV 2022-3-25
Hi all, I'm relatively new to MATLAB, and have been writing an algorithm for some time now. I've run into a problem where a function S(t,x) is the summation of another function. Below is the code and I'll explain more after:
t = linspace(0,2*pi,9);
x = linspace(-0.5,0.5,5);
Coords = combvec(t,x)'; % Creates the combination of all t with all x
% Finding the set N1
for i = 1:length(Coords)
if (Coords(i,2)>0)
N1(i,j) = Coords(i,j)
end
end
N1 = N1(any(N1,2),:);
This creates a vector of coordinates (t,x) which we want to use. I essentally want to find the below function using all coordinates (tj,xj) from this set N1.
I've tried writing the following but it's clearly wrong and not sure what to do: (note that fj is another function that depends only on these points inside the set N1.
for j = 1:length(N1)
tj = N1(j,1)
xj = N1(j,2)
fj = sin(tj)-sign(xj)
S1 = @(t,x) sum((-56*(1-sqrt((x-xj)^2+(t-tj)^2))^6*(35*sqrt((x-xj)^2+(t-tj)^2)^2+18*sqrt((x-xj)^2+(t-tj)^2)+3)*((xj-x)*fj+(tj-t))))
end
Any help would be highly appreciated.
  2 个评论
VBBV
VBBV 2022-3-24
Note that your t and x vectors are not of same length. You need to make them equal in order to add.
t = linspace(0,2*pi,9);
x = linspace(-0.5,0.5,9);% here
Jordan Boote
Jordan Boote 2022-3-25
The combvec takes care of this though I think as what we want is every t value paired with all x values. So instead of having 9 coordinates we have many more.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

VBBV
VBBV 2022-3-24
编辑：VBBV 2022-3-24
for j = 1:length(N1)
% remaining code here
S1 = @(t,x) ((-56.*(1-sqrt((x-xj).^2+(t-tj).^2)).^6.*(35*sqrt((x-xj).^2+(t-tj).^2).^2+18*sqrt((x-xj).^2+(t-tj).^2)+3).*((xj-x).*fj+(tj-t))))
S11(j,:) = S1(t,x);% assuming t and x are defined as earlier
end
S11 = sum(S11(:,:))
You can sum S1 outside of loop after computing it.
  2 个评论
VBBV
VBBV 2022-3-25
编辑：VBBV 2022-3-25
Ran in:
t = linspace(0,2*pi,9);
x = linspace(-0.5,0.5,9); % this is important change
Coords = combvec(t,x)' % Creates the combination of all t with all x
Coords = 81×2
0 -0.5000 0.7854 -0.5000 1.5708 -0.5000 2.3562 -0.5000 3.1416 -0.5000 3.9270 -0.5000 4.7124 -0.5000 5.4978 -0.5000 6.2832 -0.5000 0 -0.3750
% Finding the set N1
for j = 1:length(Coords)
if (Coords(j,2)>0)
N1(j,:) = Coords(j,:);
end
end
N1 = N1(any(N1,2),:);
for j = 1:length(N1)
tj = N1(j,1);
xj = N1(j,2);
fj = sin(tj)-sign(xj);
S1 = @(t,x) ((-56.*(1-sqrt((x-xj).^2+(t-tj).^2)).^6.*(35*sqrt((x-xj).^2+(t-tj).^2).^2+18*sqrt((x-xj).^2+(t-tj).^2)+3).*((xj-x).*fj+(tj-t))));
S11(j,:) = S1(t,x);% assuming t and x are defined as earlier
end
S11 = sum(S11(:,:))
S11 = 1×9
1.0e+10 * -5.4988 -1.3410 -0.2565 -0.0345 0.0006 0.0391 0.2807 1.4496 5.9341

请先登录，再进行评论。

更多回答（1 个）

David Hill
David Hill 2022-3-24
No need for for-loop
t = linspace(0,2*pi,9);
x = linspace(-0.5,0.5,5);
[T,X]=meshgrid(t,x);
fj = sin(T)-sign(X);
S = @(t,x) sum((-56*(1-sqrt((x-X).^2+(t-T).^2)).^6.*(35*sqrt((x-X).^2+(t-T).^2).^2+18*sqrt((x-X).^2+(t-T).^2)+3).*((X-x).*fj+(T-t))),'all');

类别

在 Help Center 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

标签

产品


版本

R2022a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by