hi, everyone! i'm doing a little program, and it would be usefull to know if the matrix the user inputs id diagonal. i know how to do a function that does so, but using a for(...;...;...) and i've seen recently that people defines functions like this: issym=@(x) all(all(x==x.')); tf=issym(mat); (this one checks if the matrix is symetric) so i would aprciate, a function that check if a matrix is diagonal, or at least some explanation for me to build it that way. thanks in advance

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12/21/2010 4:07:24 PM

Perhaps this, isdiag=@(A) ~nnz(A-spdiags(diag(A),0,size(A,1)));

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12/21/2010 4:47:05 PM

"Matt J" wrote in message <ieqlm9$90l$1@fred.mathworks.com>... > Perhaps this, > > isdiag=@(A) ~nnz(A-spdiags(diag(A),0,size(A,1))); Hey, thanks for the answer, but i tried it and didn't work the function: function [ res ] = is_diagonal( mat ) isdiag=@(A) ~nnz(A-spdiags(diag(A),0,size(A,1))); res=isdiag(mat); end in the terminal: m2 = 1 0 0 0 2 0 0 0 3 >> is_diagonal(m2) ans = 0

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12/21/2010 5:58:08 PM

Make that sdiag=@(A) ~nnz(A-spdiags(diag(A),0,speye(size(A,1))));

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12/21/2010 6:14:07 PM

"santi" wrote in message <ieqjbs$7g4$1@fred.mathworks.com>... > hi, everyone! > > i'm doing a little program, and it would be usefull to know if the matrix the user inputs id diagonal. > > i know how to do a function that does so, but using a for(...;...;...) and i've seen > recently that people defines functions like this: > > issym=@(x) all(all(x==x.')); > tf=issym(mat); > > (this one checks if the matrix is symetric) > > so i would aprciate, a function that check if a matrix is diagonal, or at least some explanation for me to build it that way. > > thanks in advance A few things could clean this up. I might check to verify that the matrix is only 2-d. And my help would be complete, with a descriptive H1 line. John function result = isdiagonal (A) % help block (yada, yada, yada) [I,J] = find(A); if ~isempty(I) result = all(I == J); else % make the simple choice that an all zero matrix % or an empty array is by definition diagonal, since % it has no non-zero off diagonals. result = true; end

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12/21/2010 6:15:23 PM

"santi" wrote in message <ieqjbs$7g4$1@fred.mathworks.com>... > hi, everyone! > > i'm doing a little program, and it would be usefull to know if the matrix the user inputs id diagonal. > > i know how to do a function that does so, but using a for(...;...;...) and i've seen > recently that people defines functions like this: > > issym=@(x) all(all(x==x.')); > tf=issym(mat); > > (this one checks if the matrix is symetric) > > so i would aprciate, a function that check if a matrix is diagonal, or at least some explanation for me to build it that way. > > thanks in advance I would suggest: isdiagonal = isequal(diag(diag(X)),X) The solutions with, for instance, find fail for cases with zeros on the diagonal ... In my opinion zeros(N) is also a valid diagonal matrix. Jos

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12/21/2010 8:18:21 PM

John's solution is the best, because it works for large matrix, straight forward, easy to understand and fast. Bruno

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12/21/2010 8:30:24 PM

I would probably recommend the following modification to John's code. The reason is that for large dense matrices, the results of find() could consume three times as much data as the original matrix. Pre-checking nnz(A)>size(A,1) can prevent a lot of unnecessary memory alloc. @Jos: checking whether the find() returns empty takes care of the zero(N) case. diag(diag(...)) seems sub-optimal from a memory alloc point of view. function result = isdiagonal (A) % help block (yada, yada, yada) if nnz(A)>size(A,1) %<----Matt J added this pre-check result=false; return [I,J] = find(A); if ~isempty(I) result = all(I == J); else % make the simple choice that an all zero matrix % or an empty array is by definition diagonal, since % it has no non-zero off diagonals. result = true; end

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12/21/2010 8:41:21 PM

"Jos (10584)" wrote in message <ier22d$p4c$1@fred.mathworks.com>... > > I would suggest: > > isdiagonal = isequal(diag(diag(X)),X) > > The solutions with, for instance, find fail for cases with zeros on the diagonal ... In my opinion zeros(N) is also a valid diagonal matrix. > > Jos I believe John's code did take into account a zeros matrix in the ELSE clause.

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12/21/2010 8:47:20 PM

Why not go ahead and make it compatible with MATLAB's DIAG function too? function [yn,k] = isdiag(A) % First return arg indicates if the input is diagonal, second indicates % which diagonal. To check for "proper diagonality" (nonzeros on the % main diagonal only) we want k = 0. yn = find(A); if isempty(yn) % If zeros is a diagonal matrix. yn = true; k = 0; return end k = yn(1); yn = all(diff(yn)==size(A,1)+1); if k>size(A,1) k = floor(k/size(A,1)); else k = -(k-1); end

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12/21/2010 9:05:24 PM

Another proposal: isdiag=@(A) nnz(A)==nnz(diag(A)) or if you want to check a particular diagonal isdiag=@(A,k) nnz(A)==nnz(diag(A,k))

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12/21/2010 9:34:07 PM

"Matt J" wrote in message <ier3dh$ljg$1@fred.mathworks.com>... > I would probably recommend the following modification to John's code. The reason is that for large dense matrices, the results of find() could consume three times as much data as the original matrix. > Pre-checking nnz(A)>size(A,1) can prevent a lot of unnecessary memory alloc. > Yes, after I posted, I realized I wanted to add that feature too. Good addition. John

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12/21/2010 9:57:05 PM

Here is a MEX file for checking a full matrix is diagonal: /************************************************************************* * Mexfile isdiagmex.c * [res] = isdiagmex(A) * * return 1 if A is a diagonal matrix * Note: sparse matrix not supported * * mex isdiagmex.c % on 32-bit * mex -largeArrayDims isdiagmex.c % on 32-bit *************************************************************************/ #include "mex.h" /* Define correct type depending on platform You might have to modify here depending on your compiler */ #if defined(_MSC_VER) || defined(__BORLANDC__) typedef __int64 int64; typedef __int32 int32; typedef __int16 int16; typedef __int8 int08; #else /* LINUX + LCC, CAUTION: not tested by the author */ typedef long long int int64; typedef long int int32; typedef short int16; typedef char int08; #endif #define A prhs[0] #define R plhs[0] #define DIAG_ENGINE(pr, pi, pAType) \ pr = (pAType*)PrA; \ pi = (pAType*)PiA; \ if (PiA==NULL) \ for (i=0; i<n; ++i) { \ if ((pr[i]!=0) && (i % m)) { \ res = 0; \ break; \ } } \ else { \ for (i=0; i<n; ++i) \ if ((pr[i]!=0 || pi[i]!=0) && (i % m)) { \ res = 0; \ break; \ } } void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { mxClassID ClassID; mwSize i, m, n; double *PrA, *PiA; double *prdouble, *pidouble; float *prsingle, *pisingle; int64 *pr64, *pi64; int32 *pr32, *pi32; int16 *pr16, *pi16; int08 *pr08, *pi08; double res = 1; if( nrhs != 1 ) mexErrMsgTxt("One arguments required."); if (mxIsSparse(A)) mexErrMsgTxt("Sparse not suppored."); m = mxGetM(A); n = mxGetN(A); n *= m; /* Get data pointers */ PrA = mxGetPr(A); PiA = mxGetPi(A); m++; /* Get class of input matrix */ ClassID = mxGetClassID(A); switch (ClassID) { case mxDOUBLE_CLASS: DIAG_ENGINE(prdouble, pidouble, double); break; case mxSINGLE_CLASS: DIAG_ENGINE(prsingle, pisingle, float); break; case mxINT64_CLASS: case mxUINT64_CLASS: DIAG_ENGINE(pr64, pi64, int64); break; case mxINT32_CLASS: case mxUINT32_CLASS: DIAG_ENGINE(pr32, pi32, int32); break; case mxCHAR_CLASS: case mxINT16_CLASS: case mxUINT16_CLASS: DIAG_ENGINE(pr16, pi16, int16); break; case mxLOGICAL_CLASS: case mxINT8_CLASS: case mxUINT8_CLASS: DIAG_ENGINE(pr08, pi08, int08); } R = mxCreateDoubleScalar(res); return; } // Bruno

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12/21/2010 9:58:07 PM

"Matt J" wrote in message <ier6gf$bld$1@fred.mathworks.com>... > Another proposal: > > isdiag=@(A) nnz(A)==nnz(diag(A)) This is very good, but it needs extra lines to take care of the case such as A = [1:10] for example. Bruno

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12/22/2010 8:09:05 AM

Dear Bruno, I think, the MEX approach is the cleanest one, because it uses a minimum of temporary memory. Some minor comments: > #if defined(_MSC_VER) || defined(__BORLANDC__) > typedef __int64 int64; > typedef __int32 int32; > ... > #else /* LINUX + LCC, CAUTION: not tested by the author */ > typedef long long int int64; > typedef long int int32; You can leave these boring definitions to "tmwtypes.h", which is included in "mex.h": int64_T, uint64_T, int32_T etc. is defined properly already. I had some strange experiences with NaNs: Although the IEEE standard defines every comparison with NaN as FALSE, some compilers fail. But is [NaN, 0; 0, NaN] a diagonal matrix? And [NaN, 0; 0, 0]? And [NaN]? And [0, NaN; NaN, 0]??? I have no idea how to treat NaN's "correctly" here. Unfortunately the MSVC2008 compiler does not offer ISNANF for FLOAT type, such that for SINGLE Matlab arrays the ugly bit checks are necessary to catch NaNs. > for (i=0; i<n; ++i) { \ > if ((pr[i]!=0) && (i % m)) My first idea was, that checking (i % m) is slower than a loop, which checks if SIZE(X,1) subsequent elements are zeros followed by a single arbitrary element. But (i %m) is evaluated only it (pr[i]!=0), which is very seldom for large arrays. Finally we'd need some numerical limit, because [1, eps; eps, 1] could be almost diagonal, diagonal or not diagonal depending on the calling algorithm. Kind regards, Jan

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12/22/2010 9:32:04 AM

Hello, I am a new beginner of Matlab and I want to create a Diagnoal Matrix with the main diagnoal as (A1,A2,A3,....,Aj) where Aj is also a matrix which is defined as (a11,a12,a13;a21,a22,a23;a31,a32,a33). How can I define Aj as a variable in the m file then create the diagnoal matrix through Aj? Could someone help on this please? Many Thanks in Advance! "Jie " <jz286@cam.ac.uk> wrote in message <h6selu$9ng$1@fred.mathworks.com>... > Hello, > > I am a new beginner of Matlab and I want to create a Diagnoal Matrix with the main diagnoal as (A1,A2,A3,....,Aj) w...

On 1/6/11 at 2:06 AM, xiaochu@gmail.com (benyaya) wrote: >What I try to do is extract the diagonal, subtract if from the >matrix, then compare the new matrix with 0. My code doesn't work out >though, can anyone help? thanks a lot. >checkIfDiagonalMatrix[m_] = Module[{d, mtemp}, >d = Dimensions[m]; >mtemp = DiagonalMatrix[Diagonal[m]] - m; >If[mtemp == Table[Table[0, {i, 1, d}], {i, 1, d}], >True, >False] >] One immediate problem is Dimensions[m] returns a list. Consequently, d cannot be used as the end point for the Table iterator. The following will do what you want and has the same logic as you have used checkIfDiagonalMatrix[m_] := Module[{d, mtemp}, d = Dimensions[m]; mtemp = DiagonalMatrix[Diagonal[m]] - m; If[mtemp == ConstantArray[0,d], True, False] ] Note, I used SetDelayed (:=) not Set (=) But I think this logic is doing more work than necessary. I would accomplish this as: diagonalQ[ m_] := (ArrayRules[SparseArray@m] /. HoldPattern[{a_, a_} -> _] :> Sequence[]) == {} If m is a diagonal matrix this should be pretty fast. However, it m is a dense array, this might be fairly slow. What I am doing is using ArrayRules to extract all of the non-zero elements of m. Those are returned as rules that look like {m,n}->number. I then apply a pattern matching rule that deletes all cases where m and n are equal and compare that to the empty list {}. ...

On 7 Jan 2011, at 10:12, Bill Rowe wrote: > On 1/6/11 at 2:06 AM, xiaochu@gmail.com (benyaya) wrote: > >> What I try to do is extract the diagonal, subtract if from the >> matrix, then compare the new matrix with 0. My code doesn't work out >> though, can anyone help? thanks a lot. > >> checkIfDiagonalMatrix[m_] = Module[{d, mtemp}, >> d = Dimensions[m]; >> mtemp = DiagonalMatrix[Diagonal[m]] - m; >> If[mtemp == Table[Table[0, {i, 1, d}], {i, 1, d}], >> True, >> False] >> ] > > One immediate probl...

The sparse-array example ran so fast (on my machine) that it doesn't matter which method you use: m = SparseArray[Band[{1, 1}] -> RandomReal[1, {10000}]]; Timing[UpperTriangularize[m] == LowerTriangularize[m]] {0.000874, True} Timing[Total[Unitize@m, 2] == Total[Unitize@Diagonal[m]]] {0.000417, True} Timing[m == DiagonalMatrix[Diagonal@m]] {0.000559, True} But that's not a general diagonal matrix, which might be something like: m = Developer`ToPackedArray@ Normal@SparseArray[Band[{1, 1}] -> RandomReal[1, {10000}]]; (THAT step was very slow!) ...

Hi everyone I want to creat a large diagonal matrix.The main diagonal elements of the diagonal matrix is a 3x3 matrix. For example I have a matrix A(3x3),now I should obtain the diagnoal matrix B(300x300),can anybody tell me how to do it? Deeply appreciate your help! Thank you in advance! Nandy Erik wrote: > > > Hi everyone > I want to creat a large diagonal matrix.The main diagonal > elements > of the diagonal matrix is a 3x3 matrix. > For example I have a matrix A(3x3),now I should obtain the diagnoal > matrix B(300x300), >Others I want to know how to create an...

Hi there, I have a code that computes Q'*D(t)*Q many times. Here Q is a fixed mxn matrix with m < n, while the diagonal matrix D depends on the iteration t. Because I have so many iterations that the operation slows done the entire process. I am wondering if there is any way to obtain Q'*D(t)*Q as fast as possible. Maybe from the result of Q'*Q or some kind of decomposition of Q'*Q? Thanks in advance! best, Gongguo "Gongguo Tang" wrote in message <ii7d79$lto$1@fred.mathworks.com>... > Hi there, > > I have a code that compute...

Hello all, I need to create a square matrix that has square block matricies along the diagonal and zeros everywhere else. That is to say, I need to create a block diagonal matrix where each submatrix is different. The overall matrix needs to have the form: M = - - | sm1 0 0 | | 0 sm2 0 | | 0 0 sm3 | - - Any advice would be greatly appreciated. Either post a reply or email me directly(phatphreak74@yahoo.ca). thanks in advance, the phreak phat phreak wrote: > Hello all, > I need to create a square matrix that has square block matricies > along the diagonal and zeros everywhere el...

Dear Group members, I'm trying to solve the following algebra problem Consider a skew-symmetric matrix of the form: B=[0,A; -At,0] where 0 stands for a null matrix and At the transpose of matrix A. Is it possible to obtain a transformation of this matrix such as the new matrix in the new coordinates would be a block diagonal matrix of the form: C=[C1,0; 0,C2] with C=Tt * B * T, being T the transformation matrix? If possible how can I obtain such a transformation matrix? Thanks, RV ...

Hi, I am using the matlab engine from a C++ program. I call engEvalString() and check for the return value, but the result is zero, even if a Matlab error (like "Undefined function or variable '...') occurs. Is there any way to find out if a Matlab error occured? Thanks, Philipp ...

Hi Suppose i have a matrix A= [1 4 5 8 7 3 6 5 2] I want to have a matrix B such each row of it has a row from A at the diagonal B=[1 4 5 0 0 0 0 0 0 0 0 0 8 7 3 0 0 0 0 0 0 0 0 0 6 5 2] how can i do it. I could do it with blkdiag but it supposes i input each row for the matrix, however i need something general since i need it for bigger matrices Thanks "matlab " <keep_smiling2100@yahoo.fr> wrote in message <jtkrgk$js0$1@newscl01ah.mathworks.com>... > Hi > Suppose i have a matrix A= [1 4 5 > 8 7 3 > 6 5 2] > I want to have a matrix B such each row of it has a row from A at the diagonal > > B=[1 4 5 0 0 0 0 0 0 > 0 0 0 8 7 3 0 0 0 > 0 0 0 0 0 0 6 5 2] > > how can i do it. I could do it with blkdiag but it supposes i input each row for the matrix, however i need something general since i need it for bigger matrices % Method 1 c = num2cell(A,2) B = blkdiag(c{:}) % Method 2 [i j] = find(A); B = accumarray([i (i-1)*size(A,2)+j], A(:)) % Method 3 [i j] = find(A); B = sparse(i, (i-1)*size(A,2)+j, A) % Bruno > % Method 1 > c = num2cell(A,2) > B = blkdiag(c{:}) > > % Method 2 > [i j] = find(A); > B = accumarray([i (i-1)*size(A,2)+j], A(:)) > > % Method 3 > [i j...

Hi, Probably a very silly question, but how can one talk about "two diagonals" of a matrix? I thought the diagonal of a matrix is M(i,i), the one going straight down the middle. Any help greatly appreciated. Bull Dog In addition to other explanations, there is this: <http://mathworld.wolfram.com/Diagonal.html> The diagonal you refer to is the 'main diagonal'. ...

How I can put time value like 10:23:34 in a matrix cell. Like below: a(1,2)= 10:23:34 Regards "M" wrote in message <kehbrk$3pp$1@newscl01ah.mathworks.com>... > How I can put time value like 10:23:34 in a matrix cell. Like below: > a(1,2)= 10:23:34 One approach is to use a cell array and have the entry be a string. E.g., a = cell(1,2); a{1,2} = '10:23:34'; James Tursa On 2/1/2013 3:46 PM, James Tursa wrote: > "M" wrote in message <kehbrk$3pp$1@newscl01ah.mathworks.com>... >> How I can put time value like 10:23:34 in a matrix cell. Like below: >> a(1,2)= 10:23:34 > > One approach is to use a cell array and have the entry be a string. E.g., > > a = cell(1,2); > a{1,2} = '10:23:34'; > And another is to use the fractional portion of a datenum representation-- >> a{1,2}=datenum('10:23:34',upper('hh:mm:ss'))- fix(datenum('10:23:34',upper('hh:mm:ss'))) a = [] [0.4330] >> datestr(a{1,2},'HH:MM:SS') ans = 10:23:34 >> -- ...

Hello, a)I need to create an M*M matrix of all zeros, except for one row on ones in the center. M in the matrix will vary from 16, 32,64,128. b)I need to repeat the above for two rows of ones.Here the two rows of ones should be seperated by four rows of zeros. Thank you, athina shah wrote: > Hello, > > a)I need to create an M*M matrix of all zeros, except for one row on > ones in the center. > > M in the matrix will vary from 16, 32,64,128. it will be pretty difficult, since you can not create the rows number 7.5, 15.5 and so one > b)I need to repeat the above ...

Hi all, Is there a non-loop way of obtaining the digonal elements Aii from a matrix A and put them in a vector? A=rand(60); vd=digonal_elements_of(A) %vd is a vector Thanks, Per Look for the 'diag'-function thomas Per S wrote: > > > Hi all, > > Is there a non-loop way of obtaining the digonal elements Aii from > a > matrix A and put them in a vector? > > A=rand(60); > vd=digonal_elements_of(A) %vd is a vector > > Thanks, > Per thomas wrote: > > > Look for > the 'diag'-function > > thomas Ok thanks, I didn't kn...

In the diagonalization operation of a matrix A. [Q Gamma] = eig(A) Q= 1.0000 0 -1.0000 0 0 1.0000 0 -1.0000 0 0 0.0000 0 0 0 0 0.0000 Gamma= -0.0113 0 0 0 0 -0.0253 0 0 0 0 -0.0113 0 0 0 0 -0.0253 "Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 1.887379e-016." It seems that the eigenvalues are not different and the diagolization is a...

Hi, I have a 200x200 matrix and I wish to write certain values (a vector of 1x200) to its diagonal. Can you suggest a way to do it without using loop? Is there any direct command to write to the diagonal of a matrix? Thanks in advance. Regards, Sandeep "Sandeep " <sandeep.gore@yahoo.com> wrote in message <fj82bo$a8b$1@fred.mathworks.com>... > Hi, > > I have a 200x200 matrix and I wish to write certain values > (a vector of 1x200) to its diagonal. Can you suggest a way > to do it without using loop? Is there any direct command > to write to t...

Hi to all, I've encountered a problem using Matlab. As I'm not very familiar with matlab, there are functions which I have not used before. What I would like to know, if there is a way to express a matrix within a matrix. For example, R= [ r1 r2 r3 ... rn] where rn=[xn yn tn] and xn, yn, tn are column of numbers. I used the following code below to express the numbers in rn as coloumns for easy referencing. xn=r(:,1); %represents the columns in the matrix yn=r(:,2); tn=r(:,3); My objective is to be able to retrieve information in the matrix easily and compare their values. Meani...

Hi everbody. First of all, I apologize for my English, so please be indulgent with me if my sentences are not grammatically correct. I have some trouble with MATLAB. I have some data in txt files that I catch like that : MFS93A1 = textread('Z:/Fichiers/MFS93.A1.txt','','headerlines',1); MFS93B1 = textread('Z:/Fichiers/MFS93.B1.txt','','headerlines',1); MFM77A1 = textread('Z:/Fichiers/MFM77.A1.txt','','headerlines',1); MFM77C1 = textread('Z:/Fichiers/MFM77.C1.txt','','headerlines',1); Then, in or...

I have a matrix of larger 4x4, and I have a smaller matrix of 2x2 and their respective row and column positions in the larger matrix. I want to assign the elements of the smaller matrix to the larger matrix on that specific row and column positions with out using any loop, I am doing so, im = zeros(4,4) r=[1 2; 3 4] c=[1 2; 3 4] indices = sub2ind(size(im),r,c); im1=ones(2,2) im(r, c)=im1(:) but it gives exception of, "Subscripted assignment dimension mismatch". any help in this regard will be appreciated. On 8/22/14, 2:20 PM, javed iqbal wrote: >...

Hi, I have a survey sample file with some 260 variables, that is repeated for 2= 1 different subgroups (this could go up to 50). Per subgroup, I create a co= rrelation matrix over all 260 variables (yes, that can be useful...). I.e.,= I use the CORR command to write out a matrix file. The goal of my intended analysis is to check the pairwise correlations for = outliers. Outliers are defined in comparison to same variable pairs across = all subgroups. Using VARSTOCASES, I can convert the matrix to long format, making all pair= s of the substantive variables the cases in the new ...

check check one twoo Stifler wrote: > check check one twoo You're supposed to say that into a microphone. Here it goes like this: "this is a test, please ignore." -- _______________________________________________________________________ Christopher R. Carlen Principal Laser/Optical Technologist Sandia National Laboratories CA USA crcarle@sandia.gov -- NOTE: Remove "BOGUS" from email address to reply. ...

Hi folks, I'm working on parallelizing some machine learning code in MATLAB. I'm using the Parallel Computing Toolbox and the parfor construct; therefore, I have certain restrictions on how I must "slice" into certain data structures accessed within the parfor (parallel for) loop. Basically, I need to reshape my training data from an (N x d) two- dimensional matrix to a fully "slicable" (N/K x d x K) matrix, where K is the number of available parallel threads (which corresponds to the number of "slicable" input data partitions). Here, I would slice among the third dimension, i.e., partitioned_data (:,:,parallel_loop_index_i). (For now, assume N is a multiple of K.) I'm usually very good with reshape, permute, shiftdim, etc., but I am having trouble making this work nicely. I could hack in something like slicable_data_partitions = cat(3, manual_partition_1, manual_partition_2, ..., manual_partition_K) but that's horrible and I was hoping for an efficient one-liner with some combination of reshape, permute, etc. Performance is important, as this will be fairly large scale, i.e., numel(data) on the order of 10^7. Note I can actually get reshape to return output int he desired dimension, however, the d data elements along the second dimension in each of the N rows are no longer in the correct order. Detailed example of desired output: [N x d, 8 x 3]: input_data = reshape(1:24, 3, 8)' % Note transpose input_data = ...

I am making a project on image processing using MATLAB Can someone please tell me how to enter a 3 d matrix I know to enter a 2d matrix. Like A=[1 2 3; 4 6 6] A= 1 2 3 4 5 6 How is 3d matrix entered shalav: <SNIP wants to create a 3d matrix... one of the many solutions: clear m m(:,:,2)=[1 2 3;4 5 6] m(:,:,1)=pi*m(:,:,2) us try help cat A = rand(4); B = rand(4); C = cat(3,A,B); Anyway MATLAB has a really nice manual, give it a try. us <us@neurol.unizh.ch> wrote: > shalav: > <SNIP wants to create a 3d matrix... > > one of...

Hey I’m a new user. I want to perform this: I have 6 matrixes A=[1,2;3;2] B=[…] C=[..] D=[..] E=[..] F=[..] I want to find the possible combinations of those matrixes taken 3 at times and calculate the product of the matrix determiners of each combination In order to find all combinations a can do: MAT={‘A’,’B’,’C’,’D’,’E’,’F’} comb=nchoosek(MAT,3) The results is: comb = 'A' 'B' 'C' 'A' 'B' 'D' 'A' 'B' 'E' 'A' 'B' 'F' 'A' 'C' &#...

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