フィルターのクリア

Vectorising a Meshgrid Coordinate Construction

3 ビュー (過去 30 日間)
ADSW121365
ADSW121365 2020 年 9 月 2 日
コメント済み: ADSW121365 2020 年 9 月 3 日
I have three coordinate arrays (file attached) of size [M x 2], where M is the number of elements and the 2 represents different points in a 1D system. To find the 3D meshed coordinates upon which I perform calculations I use code of the form:
for ele = 1:size(X_co,1) %Loop Over Each Element
[X_cube,Y_cube,Z_cube] = meshgrid(X_co(ele,:),Y_co(ele,:),Z_co(ele,:)); %Construct Meshgrid of size [2x2x2] for an Element
X_save(:,:,:,element) = X_cube; %Save Coordinates
Y_save(:,:,:,element) = Y_cube;
Z_save(:,:,:,element) = Z_cube;
end
The solution then is of size [2x2x2xM]. My best attempt to vectorise this was:
[X_cube,Y_cube,Z_cube] = meshgrid(X_co,Y_co,Z_co);
X_save = reshape(X_cube,2,2,2,[]); Y_save = reshape(Y_cube,2,2,2,[]); Z_save = reshape(Z_cube,2,2,2,[]);
However this solution is of size [2x2x2x(M^3)] which, when plotting both solutions has many many many repeated points so doesn't actually work for my application.
Can this problem be vectorised, or is a for loop the best way to construct this coordinate array?
  3 件のコメント
jessupj
jessupj 2020 年 9 月 2 日
ndgrid is the way to go here i think. i think it can be done using meshgrid along with some resize + repmat statements.
ADSW121365
ADSW121365 2020 年 9 月 2 日
編集済み: ADSW121365 2020 年 9 月 2 日
This maybe niave implementation, but:
[XO,YO,ZO] = ndgrid(X_co,Y_co,Z_co)
seems to give the same solution as:
[X_cube,Y_cube,Z_cube] = meshgrid(X_co,Y_co,Z_co);
X_save = reshape(X_cube,2,2,2,[]); Y_save = reshape(Y_cube,2,2,2,[]); Z_save = reshape(Z_cube,2,2,2,[]);
which isn't what I'm looking for. Could you guys elaborate a little more please? (Some example arrays are attached to the main post)

サインインしてコメントする。

採用された回答

Bruno Luong
Bruno Luong 2020 年 9 月 2 日
編集済み: Bruno Luong 2020 年 9 月 2 日
One way
[~,nx] = size(X_co);
[~,ny] = size(Y_co);
[m,nz] = size(Z_co);
[NX,NY,NZ] = meshgrid(1:nx,1:ny,1:nz);
sz = [size(NX),m];
% if you know nx, ny, nz are 2 you can replace the 5 above commands by
% [NX,NY,NZ] = meshgrid(1:2);
% sz = [2,2,2,m];
X_save = X_co.';
Y_save = Y_co.';
Z_save = Z_co.';
X_save = reshape(X_save(NX,:),sz);
Y_save = reshape(Y_save(NY,:),sz);
Z_save = reshape(Z_save(NZ,:),sz);
Note: I honestly prefer your for-loop if you add a preallocation
  6 件のコメント
Bruno Luong
Bruno Luong 2020 年 9 月 3 日
"So by properly allocate you mean initialise the arrays as zeros before the for loop starts?"
Yes intiialize the 3 zeros arrays with SZ from with my code.
ADSW121365
ADSW121365 2020 年 9 月 3 日
Thanks, I was just checking my indexing wasn't the allocation issue.

サインインしてコメントする。

その他の回答 (0 件)

カテゴリ

Help Center および File ExchangeLoops and Conditional Statements についてさらに検索

製品


リリース

R2020a

Community Treasure Hunt

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

Start Hunting!

Translated by