Finding closest points to a given range in matrix

2011 12 13
4 个回答
回答已采纳
2 次查看（30 天）

1 个投票

Hi,
I have a 3 column matrix, x,y,and z respectively. I want to obtain the value of z corresponds to (closest point to 0.00 in x), and closest point to 0.29 in y) (both conditions must be satisfied in the same row).
To sum , for example, x range is between 0.00 and 0.02, and that of y is between 0.28 and 0.29). At the end, I may obtain the values as x=0.0005, its corresponding y=0.28 and (z=-0.3355)
I investigated in the forum but could not find a solution. Could you kindly give me some advice for this?
Thanks in advance.

请先登录，再回答此问题。

 采纳的回答

Sean de Wolski
Sean de Wolski 2011-12-13

0 个投票

A =[ 0.375 0.279 0.366
0.004 0.256 0.321
0.004 0.266 0.322
0.004 0.276 0.333
0.004 0.286 0.338
0.004 -0.687 0.211
0.004 -0.677 0.216
0.486 -0.687 0.201
0.787 -0.697 0.146
1.168 -1.229 0.050
-0.588 -0.587 0.080
-0.678 -0.988 0.036
-0.839 0.065 0.062];
To find the minimum sum of absolute differences.
goal = [0 0.28];
[~, idx] = min(sum(abs(bsxfun(@(minus,A(:,1:2),goal)),2));
A(idx,:)
To find the minimum vector magnitude in 2d space:
goal = [0 0.28];
r = bsxfun(@minus,A(:,1:2),goal);
[~, idx] = min(hypot(r(:,1),r(:,2)));
A(idx,:)

更多回答（3 个）

Fangjun Jiang
Fangjun Jiang 2011-12-13

0 个投票

The closet point to 0 in x might have one point. The closet point to 0.29 might also have one point. What if they are not in the same row? Does't it mean you don't have a solution.
xyz=rand(20,3);
[MinX,Indx]=min(abs(xyz(:,1)))
[MinY,IndY]=min(abs(xyz(:,2)-0.29));
if MinX~=MinY
disp('no solutin');
else
FoundZ=xyz(IndX,3);
end
Mads
Mads 2011-12-13

0 个投票

If A is your matrix you could use:
[~,b] = min(abs(A(:,1))+abs(A(:,2)-0.29))
where b is the rows position which satisfies being the minimum absolute distance to the point.
tethys
tethys 2011-12-13

0 个投票

First of all, thank you for your time.
I tried both of them , but "there is no solution". Yet, for instance when I evaluate my data I have [0,0040 0,2759 -0,3329], I want to obtain data like this x is closest to zero, y is closest to 0.29 (intersection)which give me z. Regarding values they do not need to be same.
I am still trying to develop your codes.

6 个评论
显示 4更早的评论 隐藏 4更早的评论

Fangjun Jiang
Fangjun Jiang 2011-12-13
Do you understand my point in my answer? Or maybe you didn't describe your question correctly. Could you provide a set of example data (the nx3 matrix) and then explain the expected output?
tethys
tethys 2011-12-13
Maybe I think I could not describe my question properly,Here is the set of data:
0,375 0,279 0,366
0,004 0,256 0,321
0,004 0,266 0,322
0,004 0,276 0,333
0,004 0,286 0,338
0,004 -0,687 0,211
0,004 -0,677 0,216
0,486 -0,687 0,201
0,787 -0,697 0,146
1,168 -1,229 0,050
-0,588 -0,587 0,080
-0,678 -0,988 0,036
-0,839 0,065 0,062
For me, I want to find "0,004 0,276 0,333", because x is closest to zero, and y is closest to 0.28.
For "0,375 0,279 0,366", y is closest to 0.28 but x is not closest to zero. It does not make sense to me.
I hope I can explain better now. Thank you again for your valuable time.
tethys
tethys 2011-12-13
The code you suggested me can find the closest for x and y for the range I aspire; x has to be closest one to zero, than y has to be closest to 0.28 but within minimum x vector.
Fangjun Jiang
Fangjun Jiang 2011-12-13
So are you looking for a point of (x,y) which is the closet to (0,0.28), which means sqrt(x^2+(y-0.28)^2)? That is different than "x close to 0" and "y close to 0.28".
tethys
tethys 2011-12-13
Yes, definetely I am looking for closest to (0, 0.28) and its corresponding z. Sorry for the confusing

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Mathematics 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