Mixing
Use of Matlab find function for getting index of a vertex using its coordinates
0
I have a matrix 50943x3 that contains vertices of a surface mesh.I want to find the index of a certain vertex using its coordinates (x,y,z).
I tried the Matlab function find but it return an empty matrix 0-by-1.
Thanks in advance,
Cheers
matlab find mesh surface vertex
asked Nov 19 '18 at 14:25
amine
73
add a comment |
0
I have a matrix 50943x3 that contains vertices of a surface mesh.I want to find the index of a certain vertex using its coordinates (x,y,z).
I tried the Matlab function find but it return an empty matrix 0-by-1.
Thanks in advance,
Cheers
matlab find mesh surface vertex
asked Nov 19 '18 at 14:25
amine
73
2
You should post your code to show what has been attempted
– Brice
Nov 19 '18 at 14:39
add a comment |
0
0
0
I have a matrix 50943x3 that contains vertices of a surface mesh.I want to find the index of a certain vertex using its coordinates (x,y,z).
I tried the Matlab function find but it return an empty matrix 0-by-1.
Thanks in advance,
Cheers
matlab find mesh surface vertex
asked Nov 19 '18 at 14:25
amine
73
I have a matrix 50943x3 that contains vertices of a surface mesh.I want to find the index of a certain vertex using its coordinates (x,y,z).
I tried the Matlab function find but it return an empty matrix 0-by-1.
Thanks in advance,
Cheers
matlab find mesh surface vertex
matlab find mesh surface vertex
asked Nov 19 '18 at 14:25
amine
73
asked Nov 19 '18 at 14:25
amine
73
asked Nov 19 '18 at 14:25
amine
73
asked Nov 19 '18 at 14:25
amine
73
asked Nov 19 '18 at 14:25
amine
73
73
2
You should post your code to show what has been attempted
– Brice
Nov 19 '18 at 14:39
add a comment |
2
You should post your code to show what has been attempted
– Brice
Nov 19 '18 at 14:39
2
2
You should post your code to show what has been attempted
– Brice
Nov 19 '18 at 14:39
You should post your code to show what has been attempted
– Brice
Nov 19 '18 at 14:39
add a comment |
2 Answers
2
active
oldest
votes
2
Your attempt probably does not work because of floating point rounding errors. You can read more about it here. You could look into the the eps function, or just use this example:
% Your matrix
M = randn(50943 , 3);
% The coordinates you are looking for
P = [0,0,0];
% Distance between all coordinates and target point
D = sqrt(sum((M - bsxfun(@minus,M,P)).^2,2));
% Closest coordinates to target
[~ , pos] = min(D);
% Display result
disp(M(pos , :))
answered Nov 19 '18 at 14:32
Zep
1,203313
pos = find(D<tol);wheretolis a suitable tolerance would work too, in place of[~ , pos] = min(D);. It will sucessfully return 2 indices if there are two matching points, and and empty array if there is none, whileminwill always return one index. It depends whether these cases may be expected or not and what should be done in that case.
– Brice
Nov 19 '18 at 14:37
I used exactly this example to understand it but it returns a Matrix dimensions must agree error at the lineD = sqrt(sum((M - P).^2,2));
– amine
Nov 19 '18 at 14:47
@amine Probably a question of Matlab version; I corrected the example to make it compatible with older versions which do not automatically expand matrices.
– Zep
Nov 19 '18 at 14:54
@Brice, OP wants to find "find the index of a certain vertex" from its coordinates, not all the vertexes close to a given point. I think the solution should only return one point! Otherwise, yes, your modification would work.
– Zep
Nov 19 '18 at 14:55
@Zep, to be picky, to get compatibility with pre-R2016b versions of Matlab, it is adviseable to replace(M-P)withbsxfun(@minus,M,P)rather than using arepmat. Performance is better and the code shorter. And it is backward-compatible down to version R2007a.
– Brice
Nov 19 '18 at 15:05
|
show 1 more comment
1
Try the following:
mat = randi(30,50943,3);
vec = [1,2,3];
% R2106b+ code
ind = find(all(mat==vec,2));
% or: explicit expansion, works with all versions
ind = find(all(bsxfun(@eq,mat,vec),2));
What it does:
== or eq will check if coordinates are equal (gives a [50943x3] bool matrix)
all will return true only if all coordinates are equal
find returns the index of all non zero elements
This works only for an exact match (hence the integer coordinates picked with randi).
Since the answer is already accepted, I'll add @Zep answer that provide a solution to get the nearest point, which seem to be what was initially sought.
[min_dist,ind_nearest] = min(sum(bsxfun(@minus,mat,vec).^2,2)); % index to the nearest point
answered Nov 19 '18 at 14:32
Brice
1,359110
Thank you very much, it works. Now, ifvecdoes not exist in thematmatrix, how to get the nearest vertex ?
– amine
Nov 19 '18 at 14:57
If you want the nearest, then use the answer from @Zep, computing the distance and looking for the minimum. This proposal will only work with an exact match (hence the example withrandiand integer coordinates)
– Brice
Nov 19 '18 at 15:05
Yep it works, thank you for the two suggestions, I will keep it in mind
– amine
Nov 19 '18 at 15:09
add a comment |
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2 Answers
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active
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2 Answers
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active
oldest
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2
Your attempt probably does not work because of floating point rounding errors. You can read more about it here. You could look into the the eps function, or just use this example:
% Your matrix
M = randn(50943 , 3);
% The coordinates you are looking for
P = [0,0,0];
% Distance between all coordinates and target point
D = sqrt(sum((M - bsxfun(@minus,M,P)).^2,2));
% Closest coordinates to target
[~ , pos] = min(D);
% Display result
disp(M(pos , :))
answered Nov 19 '18 at 14:32
Zep
1,203313
pos = find(D<tol);wheretolis a suitable tolerance would work too, in place of[~ , pos] = min(D);. It will sucessfully return 2 indices if there are two matching points, and and empty array if there is none, whileminwill always return one index. It depends whether these cases may be expected or not and what should be done in that case.
– Brice
Nov 19 '18 at 14:37
I used exactly this example to understand it but it returns a Matrix dimensions must agree error at the lineD = sqrt(sum((M - P).^2,2));
– amine
Nov 19 '18 at 14:47
@amine Probably a question of Matlab version; I corrected the example to make it compatible with older versions which do not automatically expand matrices.
– Zep
Nov 19 '18 at 14:54
@Brice, OP wants to find "find the index of a certain vertex" from its coordinates, not all the vertexes close to a given point. I think the solution should only return one point! Otherwise, yes, your modification would work.
– Zep
Nov 19 '18 at 14:55
@Zep, to be picky, to get compatibility with pre-R2016b versions of Matlab, it is adviseable to replace(M-P)withbsxfun(@minus,M,P)rather than using arepmat. Performance is better and the code shorter. And it is backward-compatible down to version R2007a.
– Brice
Nov 19 '18 at 15:05
|
show 1 more comment
2
Your attempt probably does not work because of floating point rounding errors. You can read more about it here. You could look into the the eps function, or just use this example:
% Your matrix
M = randn(50943 , 3);
% The coordinates you are looking for
P = [0,0,0];
% Distance between all coordinates and target point
D = sqrt(sum((M - bsxfun(@minus,M,P)).^2,2));
% Closest coordinates to target
[~ , pos] = min(D);
% Display result
disp(M(pos , :))
answered Nov 19 '18 at 14:32
Zep
1,203313
pos = find(D<tol);wheretolis a suitable tolerance would work too, in place of[~ , pos] = min(D);. It will sucessfully return 2 indices if there are two matching points, and and empty array if there is none, whileminwill always return one index. It depends whether these cases may be expected or not and what should be done in that case.
– Brice
Nov 19 '18 at 14:37
I used exactly this example to understand it but it returns a Matrix dimensions must agree error at the lineD = sqrt(sum((M - P).^2,2));
– amine
Nov 19 '18 at 14:47
@amine Probably a question of Matlab version; I corrected the example to make it compatible with older versions which do not automatically expand matrices.
– Zep
Nov 19 '18 at 14:54
@Brice, OP wants to find "find the index of a certain vertex" from its coordinates, not all the vertexes close to a given point. I think the solution should only return one point! Otherwise, yes, your modification would work.
– Zep
Nov 19 '18 at 14:55
@Zep, to be picky, to get compatibility with pre-R2016b versions of Matlab, it is adviseable to replace(M-P)withbsxfun(@minus,M,P)rather than using arepmat. Performance is better and the code shorter. And it is backward-compatible down to version R2007a.
– Brice
Nov 19 '18 at 15:05
|
show 1 more comment
2
2
2
Your attempt probably does not work because of floating point rounding errors. You can read more about it here. You could look into the the eps function, or just use this example:
% Your matrix
M = randn(50943 , 3);
% The coordinates you are looking for
P = [0,0,0];
% Distance between all coordinates and target point
D = sqrt(sum((M - bsxfun(@minus,M,P)).^2,2));
% Closest coordinates to target
[~ , pos] = min(D);
% Display result
disp(M(pos , :))
answered Nov 19 '18 at 14:32
Zep
1,203313
Your attempt probably does not work because of floating point rounding errors. You can read more about it here. You could look into the the eps function, or just use this example:
% Your matrix
M = randn(50943 , 3);
% The coordinates you are looking for
P = [0,0,0];
% Distance between all coordinates and target point
D = sqrt(sum((M - bsxfun(@minus,M,P)).^2,2));
% Closest coordinates to target
[~ , pos] = min(D);
% Display result
disp(M(pos , :))
answered Nov 19 '18 at 14:32
Zep
1,203313
edited Nov 19 '18 at 15:10
answered Nov 19 '18 at 14:32
Zep
1,203313
answered Nov 19 '18 at 14:32
Zep
1,203313
answered Nov 19 '18 at 14:32
Zep
1,203313
1,203313
pos = find(D<tol);wheretolis a suitable tolerance would work too, in place of[~ , pos] = min(D);. It will sucessfully return 2 indices if there are two matching points, and and empty array if there is none, whileminwill always return one index. It depends whether these cases may be expected or not and what should be done in that case.
– Brice
Nov 19 '18 at 14:37
I used exactly this example to understand it but it returns a Matrix dimensions must agree error at the lineD = sqrt(sum((M - P).^2,2));
– amine
Nov 19 '18 at 14:47
@amine Probably a question of Matlab version; I corrected the example to make it compatible with older versions which do not automatically expand matrices.
– Zep
Nov 19 '18 at 14:54
@Brice, OP wants to find "find the index of a certain vertex" from its coordinates, not all the vertexes close to a given point. I think the solution should only return one point! Otherwise, yes, your modification would work.
– Zep
Nov 19 '18 at 14:55
@Zep, to be picky, to get compatibility with pre-R2016b versions of Matlab, it is adviseable to replace(M-P)withbsxfun(@minus,M,P)rather than using arepmat. Performance is better and the code shorter. And it is backward-compatible down to version R2007a.
– Brice
Nov 19 '18 at 15:05
|
show 1 more comment
pos = find(D<tol);wheretolis a suitable tolerance would work too, in place of[~ , pos] = min(D);. It will sucessfully return 2 indices if there are two matching points, and and empty array if there is none, whileminwill always return one index. It depends whether these cases may be expected or not and what should be done in that case.
– Brice
Nov 19 '18 at 14:37
I used exactly this example to understand it but it returns a Matrix dimensions must agree error at the lineD = sqrt(sum((M - P).^2,2));
– amine
Nov 19 '18 at 14:47
@amine Probably a question of Matlab version; I corrected the example to make it compatible with older versions which do not automatically expand matrices.
– Zep
Nov 19 '18 at 14:54
@Brice, OP wants to find "find the index of a certain vertex" from its coordinates, not all the vertexes close to a given point. I think the solution should only return one point! Otherwise, yes, your modification would work.
– Zep
Nov 19 '18 at 14:55
@Zep, to be picky, to get compatibility with pre-R2016b versions of Matlab, it is adviseable to replace(M-P)withbsxfun(@minus,M,P)rather than using arepmat. Performance is better and the code shorter. And it is backward-compatible down to version R2007a.
– Brice
Nov 19 '18 at 15:05
pos = find(D<tol); where tol is a suitable tolerance would work too, in place of [~ , pos] = min(D);. It will sucessfully return 2 indices if there are two matching points, and and empty array if there is none, while min will always return one index. It depends whether these cases may be expected or not and what should be done in that case.– Brice
Nov 19 '18 at 14:37
pos = find(D<tol); where tol is a suitable tolerance would work too, in place of [~ , pos] = min(D);. It will sucessfully return 2 indices if there are two matching points, and and empty array if there is none, while min will always return one index. It depends whether these cases may be expected or not and what should be done in that case.– Brice
Nov 19 '18 at 14:37
I used exactly this example to understand it but it returns a Matrix dimensions must agree error at the line
D = sqrt(sum((M - P).^2,2));– amine
Nov 19 '18 at 14:47
I used exactly this example to understand it but it returns a Matrix dimensions must agree error at the line
D = sqrt(sum((M - P).^2,2));– amine
Nov 19 '18 at 14:47
@amine Probably a question of Matlab version; I corrected the example to make it compatible with older versions which do not automatically expand matrices.
– Zep
Nov 19 '18 at 14:54
@amine Probably a question of Matlab version; I corrected the example to make it compatible with older versions which do not automatically expand matrices.
– Zep
Nov 19 '18 at 14:54
@Brice, OP wants to find "find the index of a certain vertex" from its coordinates, not all the vertexes close to a given point. I think the solution should only return one point! Otherwise, yes, your modification would work.
– Zep
Nov 19 '18 at 14:55
@Brice, OP wants to find "find the index of a certain vertex" from its coordinates, not all the vertexes close to a given point. I think the solution should only return one point! Otherwise, yes, your modification would work.
– Zep
Nov 19 '18 at 14:55
@Zep, to be picky, to get compatibility with pre-R2016b versions of Matlab, it is adviseable to replace
(M-P) with bsxfun(@minus,M,P) rather than using a repmat. Performance is better and the code shorter. And it is backward-compatible down to version R2007a.– Brice
Nov 19 '18 at 15:05
@Zep, to be picky, to get compatibility with pre-R2016b versions of Matlab, it is adviseable to replace
(M-P) with bsxfun(@minus,M,P) rather than using a repmat. Performance is better and the code shorter. And it is backward-compatible down to version R2007a.– Brice
Nov 19 '18 at 15:05
|
show 1 more comment
1
Try the following:
mat = randi(30,50943,3);
vec = [1,2,3];
% R2106b+ code
ind = find(all(mat==vec,2));
% or: explicit expansion, works with all versions
ind = find(all(bsxfun(@eq,mat,vec),2));
What it does:
== or eq will check if coordinates are equal (gives a [50943x3] bool matrix)
all will return true only if all coordinates are equal
find returns the index of all non zero elements
This works only for an exact match (hence the integer coordinates picked with randi).
Since the answer is already accepted, I'll add @Zep answer that provide a solution to get the nearest point, which seem to be what was initially sought.
[min_dist,ind_nearest] = min(sum(bsxfun(@minus,mat,vec).^2,2)); % index to the nearest point
answered Nov 19 '18 at 14:32
Brice
1,359110
Thank you very much, it works. Now, ifvecdoes not exist in thematmatrix, how to get the nearest vertex ?
– amine
Nov 19 '18 at 14:57
If you want the nearest, then use the answer from @Zep, computing the distance and looking for the minimum. This proposal will only work with an exact match (hence the example withrandiand integer coordinates)
– Brice
Nov 19 '18 at 15:05
Yep it works, thank you for the two suggestions, I will keep it in mind
– amine
Nov 19 '18 at 15:09
add a comment |
1
Try the following:
mat = randi(30,50943,3);
vec = [1,2,3];
% R2106b+ code
ind = find(all(mat==vec,2));
% or: explicit expansion, works with all versions
ind = find(all(bsxfun(@eq,mat,vec),2));
What it does:
== or eq will check if coordinates are equal (gives a [50943x3] bool matrix)
all will return true only if all coordinates are equal
find returns the index of all non zero elements
This works only for an exact match (hence the integer coordinates picked with randi).
Since the answer is already accepted, I'll add @Zep answer that provide a solution to get the nearest point, which seem to be what was initially sought.
[min_dist,ind_nearest] = min(sum(bsxfun(@minus,mat,vec).^2,2)); % index to the nearest point
answered Nov 19 '18 at 14:32
Brice
1,359110
Thank you very much, it works. Now, ifvecdoes not exist in thematmatrix, how to get the nearest vertex ?
– amine
Nov 19 '18 at 14:57
If you want the nearest, then use the answer from @Zep, computing the distance and looking for the minimum. This proposal will only work with an exact match (hence the example withrandiand integer coordinates)
– Brice
Nov 19 '18 at 15:05
Yep it works, thank you for the two suggestions, I will keep it in mind
– amine
Nov 19 '18 at 15:09
add a comment |
1
1
1
Try the following:
mat = randi(30,50943,3);
vec = [1,2,3];
% R2106b+ code
ind = find(all(mat==vec,2));
% or: explicit expansion, works with all versions
ind = find(all(bsxfun(@eq,mat,vec),2));
What it does:
== or eq will check if coordinates are equal (gives a [50943x3] bool matrix)
all will return true only if all coordinates are equal
find returns the index of all non zero elements
This works only for an exact match (hence the integer coordinates picked with randi).
Since the answer is already accepted, I'll add @Zep answer that provide a solution to get the nearest point, which seem to be what was initially sought.
[min_dist,ind_nearest] = min(sum(bsxfun(@minus,mat,vec).^2,2)); % index to the nearest point
answered Nov 19 '18 at 14:32
Brice
1,359110
Try the following:
mat = randi(30,50943,3);
vec = [1,2,3];
% R2106b+ code
ind = find(all(mat==vec,2));
% or: explicit expansion, works with all versions
ind = find(all(bsxfun(@eq,mat,vec),2));
What it does:
== or eq will check if coordinates are equal (gives a [50943x3] bool matrix)
all will return true only if all coordinates are equal
find returns the index of all non zero elements
This works only for an exact match (hence the integer coordinates picked with randi).
Since the answer is already accepted, I'll add @Zep answer that provide a solution to get the nearest point, which seem to be what was initially sought.
[min_dist,ind_nearest] = min(sum(bsxfun(@minus,mat,vec).^2,2)); % index to the nearest point
answered Nov 19 '18 at 14:32
Brice
1,359110
edited Nov 19 '18 at 15:10
answered Nov 19 '18 at 14:32
Brice
1,359110
answered Nov 19 '18 at 14:32
Brice
1,359110
answered Nov 19 '18 at 14:32
Brice
1,359110
1,359110
Thank you very much, it works. Now, ifvecdoes not exist in thematmatrix, how to get the nearest vertex ?
– amine
Nov 19 '18 at 14:57
If you want the nearest, then use the answer from @Zep, computing the distance and looking for the minimum. This proposal will only work with an exact match (hence the example withrandiand integer coordinates)
– Brice
Nov 19 '18 at 15:05
Yep it works, thank you for the two suggestions, I will keep it in mind
– amine
Nov 19 '18 at 15:09
add a comment |
Thank you very much, it works. Now, ifvecdoes not exist in thematmatrix, how to get the nearest vertex ?
– amine
Nov 19 '18 at 14:57
If you want the nearest, then use the answer from @Zep, computing the distance and looking for the minimum. This proposal will only work with an exact match (hence the example withrandiand integer coordinates)
– Brice
Nov 19 '18 at 15:05
Yep it works, thank you for the two suggestions, I will keep it in mind
– amine
Nov 19 '18 at 15:09
Thank you very much, it works. Now, if
vec does not exist in the mat matrix, how to get the nearest vertex ?– amine
Nov 19 '18 at 14:57
Thank you very much, it works. Now, if
vec does not exist in the mat matrix, how to get the nearest vertex ?– amine
Nov 19 '18 at 14:57
If you want the nearest, then use the answer from @Zep, computing the distance and looking for the minimum. This proposal will only work with an exact match (hence the example with
randi and integer coordinates)– Brice
Nov 19 '18 at 15:05
If you want the nearest, then use the answer from @Zep, computing the distance and looking for the minimum. This proposal will only work with an exact match (hence the example with
randi and integer coordinates)– Brice
Nov 19 '18 at 15:05
Yep it works, thank you for the two suggestions, I will keep it in mind
– amine
Nov 19 '18 at 15:09
Yep it works, thank you for the two suggestions, I will keep it in mind
– amine
Nov 19 '18 at 15:09
add a comment |
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You should post your code to show what has been attempted
– Brice
Nov 19 '18 at 14:39