Hello guys, I need help.

2 次查看（过去 30 天）
Everton Silva
Everton Silva 2020-3-27
评论： Rik 2020-3-28
I need to evaluate the function in each combination of (x1, x2, x3), that is:
for i=1:11
for j=1:11
for k=1:11
z(i,j,k)=feval(f,x1(i),x2(j),x3(k));
end
end
end
This evaluation gives us an NxNxN matrix (cell?). I don't know what it's called hahahaha
[sfx, ind]=sort(z(:));
we selected the t smallest function values
sfx=sfx(1:t);
And the indexes corresponding to the t smallest function values
ind=ind(1:t);
Does anyone have any idea how I can return the values of x1, x2 and x3 corresponding to these t smallest function values?
  4 个评论
显示 2更早的评论
Guillaume
Guillaume 2020-3-27
Notes:
z(i,j,k)=feval(f,x1(i),x2(j),x3(k));
can be written more simply as
z(i,j,k)=f(x1(i),x2(j),x3(k));
assuming that f is a function handle.
Also, depending on f you may not need the loops at all.
Steven Lord
Steven Lord 2020-3-27
To compute the smallest values you can use the mink function.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Rik
Rik 2020-3-27
编辑：Rik 2020-3-28
The indices you get in your last operation can be converted to subscripts, which will correspond to your three inputs.
ind=ind(1:t);
[x1_ind,x2_ind,x3_ind]=ind2sub(size(z),ind);
x1=x1(x1_ind);
x2=x1(x2_ind);
x3=x1(x3_ind);
  4 个评论
显示 2更早的评论
Everton Silva
Everton Silva 2020-3-27
Thank you so much.
Rik
Rik 2020-3-28
@Walter thanks for catching the mistake
@Everton you're welcome

请先登录，再进行评论。

更多回答（1 个）

Torsten
Torsten 2020-3-27
编辑：Torsten 2020-3-27
[X1,X2,X3]=ndgrid(x1,x2,x3);
Z=f(X1,X2,X3); %assumes f is vectorized
M=[X1,X2,X3,Z];
[~,idx]=sort(M(:,4));
sortedM=M(idx,:);
X1s=sortedM(1:s,1);
X2s=sortedM(1:s,2);
X3s=sortedM(1:s,3);
  1 个评论
Everton Silva
Everton Silva 2020-3-27
For example, if I write in the command window
t=11;
f=@(x1,x2,x3)(x1+x2+x3);
x1=0:0.1:1;
x2=0:0.1:1;
x3=0:0.1:1;
[X1,X2,X3]=ndgrid(x1,x2,x3);
Z=f(X1,X2,X3);
M=[X1,X2,X3,Z];
[~,idx]=sort(M(:,4));
sortedM=M(idx,:);
X1s=sortedM(1:t,1);
X2s=sortedM(1:t,2);
X3s=sortedM(1:t,3);
X=[X1s,X2s,X1s]
returns
X=
0 0 0
0.1000 0.1000 0.1000
0.2000 0.2000 0.2000
0.3000 0.3000 0.3000
0.4000 0.4000 0.4000
0.5000 0.5000 0.5000
0.6000 0.6000 0.6000
0.7000 0.7000 0.7000
0.8000 0.8000 0.8000
0.9000 0.9000 0.9000
1.0000 1.0000 1.0000

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Logical 的更多信息

标签

Community Treasure Hunt

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

Start Hunting!

Translated by