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• Matrix class source files - 11 Kb

Overview

Matrices, do you hate them? I do, and they turn up all over the place in the projects I work with. So over time I have developed a class CMatrix to handle all the things we need, and some I expect to need in the future.

How the data is handled

First lets take an overview of how the class handles the data. The matrix data is allocated in a flat array of doubles with an integer reference counter at the end of the array. As the matrix is dynamic, we use a reference count system to avoid efficiency hits when assigning/copying one matrix into another. Two object can point to the same data, and they only diverge when one of them changes the data, getting its own copy of the data at that point. The data is only deleted when the last reference to it is being deleted. This has advantages for objects returned by function calls by value, and which are assigned by operator=, as there is little penalty in assigning a pointer compared to a new/copy operation.

Serialization

The CMatrix class inherits directly from CObject and is full serialization compatible.

CMatrixHelper

A small helper class has been added to allow a simulated CMatrix::operator[][] to work. I stole this idea shamelessly from Alex Chirokov's article 2D Matrix Container with [][] indexing. A nice way of doing it. Note also that you should not be creating any objects of this type in your own code. It is used for this purpose only.

Robustness

In DEBUG mode, the code compiles with 0 warnings/errors and has extensive ASSERTion checking through out, so it should catch any problems that you have (or I have) in code. Most of the functionality has been thoroughly checked, but I would recommend checking your results, just in case!

Constructors

You can construct a matrix object using the following methods:

• CMatrix() Constructs a 1 * 1 array, this is the default constructor.
• CMatrix(CMatrix& other) Copy constructor
• CMatrix(nCols, nRows) Constructs a matrix of nCols * nRows dimensions. All data is 0.
• CMatrix(size, diagonal) Constructs a square matrix with or without 1's on the diagonal.
• CMatrix(VARIANT) Constructs a CMatrix object from a 2 dimension SAFEFARRAY variant.

As a note, any non-initialized matrix elements will be set to 0 on construction.

Operators overloaded

The following operators have been overloaded:

• operator=(CMatrix) For standard assignment.

Arithmatic

• operator+(CMatrix) Adds 2 matrices together, must be the same size
• operator-(CMatrix) Subtracts 1 matrix from another, must be the same size
• operator*(CMatrix) Multiples 2 matrices together, the two inner dimensions must be the same, e.g. 3*2 by 2*3
• operator+=(CMatrix) Adds one matrix onto the current matrix, must have same dimensions.
• operator-=(CMatrix) Subtracts one matrix from the current matrix, must have same dimensions.
• operator*=(CMatrix) Mutiples the current matrix by the other matrix
• operator*=(double) Multiples all matrix elements by the given value
• operator*(CMatrix, double) Multiples all elements by the given value, returning a new matrix

Comparison

• operator==(CMatrix) For matrix comparison, returns true if identical, false otherwise.

Element access

• operator[](int) Works with the class CMatrixHelper to simulate a operator[][].

Get/Set functions

Two standard access function are provided.:

• GetElement(nCol, nRow) returns the given element value
• SetElement(nCol, nRow, value) Sets the given element to a different value

Other matrix functions

• GetNumColumns() Returns the matrices columns dimension
• GetNumRows() Returns the matrices rows dimension
• SumColumn(column) Returns the sum of all elements in the given column
• SumRow(row) Returns the sum of all elements in the given row
• SumColumnSquared(column) Same as SumColumn() but the return value is squared
• SumRowSquared(row) Same as SumRow() but the return value is squared
• GetNumericRange(min, max) Returns the lower and upper values of elements in the matrix
• GetSafeArray() Returns a VARIANT with a copy of the CMatrix data in a SAFEARRAY. Note that the VARIANT should be cleared using VariantClear(var) unless you pass the VARIANT to a different program (e.g. a COM component/VB) as it becomes their responsibility.
• CopyToClipboard() Places the CMatrix data in the clipboard as CSV text, use this when debugging etc
• WriteAsCSVFile(filename) Writes the matrix to a CSV file
• ReadFromCSVFile(const CString& filename) Creates a new matrix from a CSV file.
• Dump() TRACEs the matrix content to the debug stream
• AssertValid() ASSERTs if the object is in an invalid state

Transposition

• GetTransposed() Returns a new matrix which is a Transpose of the one called on
• Transpose() Transposes the current matrix

Inversion

• GetInverted() Returns the inversion of the current matrix
• Invert() Inverts the current matrix

Covariant (A' * A)

• Covariant() Returns the Covariant of the current matrix

Normalisation

• GetNormalised(min, max) Returns the matrix with all values scaled between min and max
• Normalise(min, max) Normalizes all values in the matrix between min and max

Concatenation

• GetConcatinatedColumns(CMatrix) Returns a new matrix with the other matrix added onto the right hand side
• ConcatinateColumns(CMatrix) Concatenates the additional columns onto the current matrix
• GetConcatenatedRows(CMatrix) Returns a new matrix with the other matrix added onto the bottom of the current matrix
• ConcatinateRows(CMatrix) Concatenates the additional rows onto the current matrix
• AddColumn(double*) Adds a new column onto the current matrix
• AddRow(double*) Adds a new row onto the current matrix

Extraction/substitution

• ExtractSubMatrix(x, y, x_size, y_size) Extract a sub matrix from a larger matrix
• SetSubMatrix(x, y, CMatrix) Substitutes a larger matrices elements with those from another matrix
• ExtractDiagonal() Returns a x * 1 matrix with the values from the diagonal - square matrices only
• GetSquareMatrix() Returns a square matrix of the smaller dimension, by stepping over rows/columns to make the matrix square
• MakeSquare() Squares the current matrix by stepping over rows/columns

Other notes

All the code to handle the allocation/deallocation of matrix data and the reference counting is not covered here in the class interface as they are all private functions. You can see the documentation in the source code comments. (wow comments....:-D)

If you find any bugs or have some enhancements for the class, I would be happy if you would pass them along, and I will endeavour to keep the class fully up to date here.

Updates

13th August 2002

• A small problem with CMatrixHelper when using operator[][] for element read access was fixed by making the return object const.
• An invalid ASSERTion error in ExtractSubMatrix was fixed.
• The operator= for CMatrixHelper now copies all member variables across into the target object.

2nd July 2002

• A small typo in CMatrix::Invert() was fixed. Thanks to Jamie Plowman for spotting it.
• As suggested, I made the class CMatrixHelper constructors protected and made CMatrix a friend so that only CMatrix can construct objects, not a user.

Enjoy!

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compile error MaryamR 2:03 22 Apr '09   I added Matrix.h and matrix.cpp to my MFC project in vc++ but it gave me over 25 errors when compliling: Error 1 error C2664: 'strcpy' : cannot convert parameter 2 from 'CString' to 'const char *' e:\thesis\projects\testimageapp\matrix.cpp 996 Error 2 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1035 Error 3 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1038 Error 4 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1041 Warning 5 warning C4996: 'CFileException::generic' was declared deprecated e:\thesis\projects\testimageapp\matrix.cpp 1043 Error 6 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1044 Error 7 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1047 Error 8 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1050 Error 9 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1053 Error 10 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1056 Error 11 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1059 Error 12 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1062 Error 13 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1065 Error 14 error C2664: 'atof' : cannot convert parameter 1 from 'CString' to 'const char *' e:\thesis\projects\testimageapp\matrix.cpp 1101 Error 15 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1133 Error 16 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1136 Error 17 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1139 Warning 18 warning C4996: 'CFileException::generic' was declared deprecated e:\thesis\projects\testimageapp\matrix.cpp 1141 Error 19 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1142 Error 20 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1145 Error 21 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1148 Error 22 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1151 Error 23 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1154 Error 24 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1157 Error 25 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1160 Error 26 error C2665: 'AfxMessageBox' : none of the 2 overloads could convert all the argument types e:\thesis\projects\testimageapp\matrix.cpp 1163 Error 27 error C2664: 'void ATL::CStringT<basetype,stringtraits>::Format(const wchar_t *,...)' : cannot convert parameter 1 from 'const char [3]' to 'const wchar_t *' e:\thesis\projects\testimageapp\matrix.cpp 1184 what is wrong with it? what should I do to fix it? Sign In·View Thread·PermaLink help me cooljeff 21:45 31 Mar '08   Hi, I can not download the sources files from the link. Can you give me a copy. My e-mail address is: whb111@uestc.edu.cn. Thanks, Best regards. Wang Hongbing Sign In·View Thread·PermaLink hi sujithkumarsl 21:36 4 Jun '07   i want to add the CNatrix class into my dll proj but its showing error. why the CObject is kept as base. can i use this class in proj other than MFC's My small attempt... Sign In·View Thread·PermaLink A better version of serialization cristitomi 0:56 15 Feb '07   Hi! Here is a better version of the serialization function for class CMatrix. The version from the original class is indeed more clear, but if you intend to use it in an application and use high order matrices this can lead to unneccessary operations, such as loops and assignments. void CMatrix::Serialize(CArchive& ar) { CObject::Serialize(ar); if(ar.IsStoring()) { // write the object header first so we can correctly recognize // the object as a CMatrix object ar << header1; ar << header2; ar << version; // write the actual matrix object ar << m_NumColumns; ar << m_NumRows; ar.Write(m_pData, sizeof(double) * m_NumColumns * m_NumRows); } else { // read the object header first so we can correctly recognize // the object type CMatrix long h1, h2; int ver; ar >> h1; ar >> h2; if(h1 != header1 || h2 != header2) { // incorrect header, cannot load matrix AfxThrowArchiveException(CArchiveException::badClass, NULL); } ar >> ver; ASSERT(ver == version); // now load the actual matrix ar >> m_NumColumns; ar >> m_NumRows; ar.Read(m_pData, sizeof(double) * m_NumColumns * m_NumRows); } } Variables header1, header2 and version are defined in "Matrix.h": #define header1 0x434d6174 #define header2 0x72697843 #define version 1 I think it's a good idea to separate the signature and version of the object beeing serialized from the serialization code so that when you modify it, you won't have to go through all the serialization code to update the values, you simply modify them where they are declared. That's it. It doesn't do much but I am working a lot with serialization and I thought that I can give a helping hand on updating this class. I am in love with VC++ Sign In·View Thread·PermaLink How to use this class in Visual C++ 6.0 cristitomi 6:32 14 Feb '07   Hi! Here is how you can use this class In Visual C++ 6.0. 1) Open Visual C++ 6.0 application. 2) Select File -> New -> Win32 Console Application. Select the desired location for your project and give it a name, let's say MatrixPrj. Click OK. 3) In the dialog box that appears select option "An application that supports MFC" and click Finish. 4) In the last step click OK to finish. 5) Copy the files "Matrix.h" and "Matrix.cpp" in your project's folder. 6) Select Project -> Add To Project -> Files. Select the files "Matrix.h" and "Matrix.cpp" and click OK. Now the two files are added to your project. 7) Go to file "Matrix.h" where CMatrixHelper class is defined, go to function void operator=(CMatrixHelper& other) and replace the following line of code: m_pMatrixConst = other.m_Col; with this one: m_pMatrixConst = other.m_pMatrixConst; 8) Now compile the entire project and you are ready to use the functionality of this class. I am in love with VC++ Sign In·View Thread·PermaLink Re: How to use this class in Visual C++ 6.0 whynot123456 21:54 31 Oct '09   How about Select File->New -> MFC AppWizard(exe) Sign In·View Thread·PermaLink Quite slow for 8x8 inverse. chueh8 9:08 21 Sep '06   It took me about 30 seconds for inverse a 8x8 matrix.. why? Might give it up if no solution for it.. Sign In·View Thread·PermaLink Eliminating the helper class cwbenson 5:15 14 Jul '06   I was interested in the suggestion of eliminating the helper class below, but as a beginner I am not sure how to implement the suggestion. Does anyone have updated matrix.h and matrix.cpp incorporating the suggestion? Hopefully it would also eliminate the error LNK2001: unresolved external symbol __endthreadex and __beginthreadex. Thank you. cwb Sign In·View Thread·PermaLink 2.00/5 link errors cwbenson 4:44 14 Jul '06   I fixed the compile error and then received the following link errors. From reading through the F1 help on LNK2001, it sounds like playing with the project compile or link settings could potentially fix the errors (or possibly produce more subtle errors). Any advice on these and possibly other problems down the road? nafxcwd.lib(thrdcore.obj) : error LNK2001: unresolved external symbol __endthreadex nafxcwd.lib(thrdcore.obj) : error LNK2001: unresolved external symbol __beginthreadex cwb Sign In·View Thread·PermaLink Error with creating CMatrix objects kimyuan81 23:39 9 Mar '06   Hi.... I tried to create a CMatrix object using CMatrix(); but the compiler could not compile saying there is errors as follows ; Linking... Global.obj : error LNK2001: unresolved external symbol "public: virtual __thiscall CMatrix::~CMatrix(void)" (??1CMatrix@@UAE@XZ) Global.obj : error LNK2001: unresolved external symbol "public: __thiscall CMatrix::CMatrix(void)" (??0CMatrix@@QAE@XZ) Debug/painter.exe : fatal error LNK1120: 2 unresolved externals Anybody that can help me resolve the following errors ?? Thanks alot cos i just started learning how to program in visual c.... Sign In·View Thread·PermaLink 1.67/5 somebody help! gampalu 5:41 14 Feb '06   Hi! I'm interested in using the matrix class, however and since I'm a newbie I don't know how to use it... can you send me a small example for Microsoft Visual C++ 6.0, creating and adding 2 matrixes? jolival@av.it.pt Thanks, Best regards, João Olival Sign In·View Thread·PermaLink Jokes wepy888 20:09 8 Dec '05   Funny Business A man is opening a restaurant and he asks one of his workers to come up with a name for it. The man tells Al, one of his workers, that he will name the resaurant after the first thing Al sees when he goes out the door. Al walks outside and the first thing he saw was a girl named Lucy and he saw her legs. He told the man, and so the restaurant was named Lucy's Legs. The man was so impressed that he said the next day Al could get a free drink. The next day Al comes a bit early and a policeman walks by and notices Al waiting there. The policeman asks, "What are you doing?" Al says, "I'm waiting for Lucy's legs to open so I can get a drink." ;P Sign In·View Thread·PermaLink I need introduce the values in matrix rubenss 7:06 18 Oct '05   Hi, How are you? Your Class Matrix is very interesting i like a lot. But i dont undenstand the way to introduce the values in matrix You put *mpData and you put that use the CMatrixHelper to simulate [][] but dont put any example Please Help me Thanks very much Sign In·View Thread·PermaLink 5.00/5 some thing is wrong chen1000 6:17 13 Oct '05   as I use the function CMatrix::Invert(),I found sometimes it doesn't work well at all,cannot calculate exactly real Invert Matrix,sometimes it is right,sometimes it is wrong,is there any problem in your programming?please check it and give me the answer Sign In·View Thread·PermaLink 1.67/5 to build cmatric zairee 23:17 6 Sep '05   to rogen allen... im very weak in c++ programming..ihope u can help me to solve my prob.. how to use cmatrix and can u give me some tutorial..then can u give me some example source code to prove eigen value and vector prob in c++ need for help Sign In·View Thread·PermaLink help..#include "stdafx.h" mohamed radwan 22:21 21 Jun '05   hi all...i m a beginner in programming..so i tried to get benifit of the code of matrix class written by Roger Allen but there was an error coz he didnt attach "stdafx.h" with his code...so if any one can help me with that...tnx Madoo Sign In·View Thread·PermaLink Complile Error terrenzhong 2:14 6 Jan '05   Can anybody help me?? When comiling the code in VC7, I've got this: Matrix.cpp(1022): error C2316: 'CFileException &' : cannot be caught as the destructor and/or copy constructor are inaccessible Thx... Sign In·View Thread·PermaLink 1.00/5 Re: Complile Error phanduchuynh 17:19 6 Jan '05   I think you should change to: CFileException*e, and e->cause Sign In·View Thread·PermaLink Problem in compiling... plz help Nagarajan S. 8:46 31 Aug '04   This is the code i am having in visual c++ 6. Matrix.h & matrix.cpp are in current project folder and included in project. #include #include "matrix.cpp" void main() { CMatrix:: A(); } But i am getting an error that matrix.h(191) :error C2440: '=' : cannot convert from 'int' to 'const class CMatrix *' Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast Please tell me what to be done. Thanks Nagarajan Sign In·View Thread·PermaLink Re: Problem in compiling... plz help Nagarajan S. 9:20 31 Aug '04   Now that probelem is correted by explicit type casting.. The program compiles without any error. #include #include "matrix.cpp" using namespace std; void main() { CMatrix A(3,4); } But while linking i get 151 errors. like Matrix.obj : error LNK2005: "public: static class CObject * __stdcall CMatrix::CreateObject(void)" (?CreateObject@CMatrix@@SGPAVCObject@@XZ) already defined in mat.obj Matrix.obj : error LNK2005: "public: virtual struct CRuntimeClass * __thiscall CMatrix::GetRuntimeClass(void)const " (?GetRuntimeClass@CMatrix@@UBEPAUCRuntimeClass@@XZ) already defined in mat.obj Matrix.obj : error LNK2005: "class CArchive & __stdcall operator>>(class CArchive &,class CMatrix * &)" (??5@YGAAVCArchive@@AAV0@AAPAVCMatrix@@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: __thiscall CMatrix::CMatrix(void)" (??0CMatrix@@QAE@XZ) already defined in mat.obj Matrix.obj : error LNK2005: "public: __thiscall CMatrix::CMatrix(class CMatrix const &)" (??0CMatrix@@QAE@ABV0@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: __thiscall CMatrix::CMatrix(int,int)" (??0CMatrix@@QAE@HH@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: __thiscall CMatrix::CMatrix(int,bool)" (??0CMatrix@@QAE@H_N@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: __thiscall CMatrix::CMatrix(struct tagVARIANT &)" (??0CMatrix@@QAE@AAUtagVARIANT@@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: virtual __thiscall CMatrix::~CMatrix(void)" (??1CMatrix@@UAE@XZ) already defined in mat.obj Matrix.obj : error LNK2005: "public: virtual void __thiscall CMatrix::Dump(class CDumpContext &)const " (?Dump@CMatrix@@UBEXAAVCDumpContext@@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: virtual void __thiscall CMatrix::AssertValid(void)const " (?AssertValid@CMatrix@@UBEXXZ) already defined in mat.obj Matrix.obj : error LNK2005: "public: virtual void __thiscall CMatrix::Serialize(class CArchive &)" (?Serialize@CMatrix@@UAEXAAVCArchive@@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "private: double * __thiscall CMatrix::AllocateMemory(int,int)" (?AllocateMemory@CMatrix@@AAEPANHH@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: class CMatrix & __thiscall CMatrix::operator=(class CMatrix const &)" (??4CMatrix@@QAEAAV0@ABV0@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: bool __thiscall CMatrix::operator==(class CMatrix const &)const " (??8CMatrix@@QBE_NABV0@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: class CMatrix __thiscall CMatrix::operator+(class CMatrix const &)const " (??HCMatrix@@QBE?AV0@ABV0@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: class CMatrix __thiscall CMatrix::operator-(class CMatrix const &)const " (??GCMatrix@@QBE?AV0@ABV0@@Z) already defined in mat.obj Matrix.obj : error LNK2005: "public: class CMatrix __thiscall CMatrix::operator*(class CMatrix const &)const " (??DCMatrix@@QBE?AV0@ABV0@@Z) already defined in mat.obj Please help me... thanks Sign In·View Thread·PermaLink operator* fix? Jonny Gould 23:58 12 Jul '04   CMatrix CMatrix::operator*(const CMatrix &other) const { // first check for a valid multiplication operation if (m_NumColumns != other.m_NumRows) throw "Matrices do not have common size" ; // now that we know that the operation is possible ASSERT(FALSE == IsBadReadPtr(other.m_pData, sizeof(double) * other.m_NumColumns * other.m_NumRows)) ; // construct the object we are going to return CMatrix result(other.m_NumColumns, m_NumRows); // e.g. // [A][B][C] [G][H] [A*G + B*I + C*K][A*H + B*J + C*L] // [D][E][F] * [I][J] = [D*G + E*I + F*K][D*H + E*J + F*L] // [K][L] // double value ; for (int i = 0 ; i < result.m_NumColumns ; i++) { for (int j = 0 ; j < result.m_NumRows ; j++) { value = 0.0 ; for (int k = 0 ; k < m_NumColumns ; k++) { value += GetElement(k,j) * other.GetElement(k,i) ; } result.SetElement(i, j, value) ; } } return result ; } Jon Gould Sign In·View Thread·PermaLink Re: operator* fix? Jonny Gould 18:46 13 Jul '04   Or even this. CMatrix CMatrix::operator*(const CMatrix &other) const { // first check for a valid multiplication operation if (m_NumColumns != other.m_NumRows) throw "Matrices do not have common size" ; // now that we know that the operation is possible ASSERT(FALSE == IsBadReadPtr(other.m_pData, sizeof(double) * other.m_NumColumns * other.m_NumRows)) ; // construct the object we are going to return CMatrix result(other.m_NumColumns, m_NumRows); // e.g. // [A][B][C] [G][H] [A*G + B*I + C*K][A*H + B*J + C*L] // [D][E][F] * [I][J] = [D*G + E*I + F*K][D*H + E*J + F*L] // [K][L] // double value ; for (int i = 0 ; i < result.m_NumColumns ; i++) { for (int j = 0 ; j < result.m_NumRows ; j++) { value = 0.0 ; for (int k = 0 ; k < m_NumColumns ; k++) { value += GetElement(k,j) * other.GetElement(i,k) ; } result.SetElement(i, j, value) ; } } return result ; } Sign In·View Thread·PermaLink Re: operator* fix? Bill Lim 22:02 7 Nov '04   In allthrough his code, the "m_NumColumns" should be "m_NumRows" and vice versa, I believe. But it works if you leave these names be. Bill^2 Sign In·View Thread·PermaLink can't compile source milan08 18:13 24 Mar '04   Hi, I think I might be missing a file or two (?), because when I compile the source, it's missing "stdafx.h" and when I comment it out I get like 50 errors (even after commenting out the MFC stuff as suggested by the author for VC++6 use) so I'm pretty sure I need that file at least. Any ideas on where I can find the misssing file(s)? -milan Sign In·View Thread·PermaLink 1.00/5 Row Reduction, Gaussian elimination, row echelon form, matrix inverse James Reilly 17:17 6 Feb '04   One thing this class is missing is an algorithm to reduce a matrix to complete row-echelon form.   Here is the algorithm from a matrix class that I wrote.   With a few very slight changes, it can be rolled into Mr. Allen's Matrix class.   This algorithm can be used to to solve systems of linear equations stored in a matrix.   It also calculates the Determinant.   You can also use this algorithm to find the inverse of a matrix. The Set & Get functions will have to be revised per Mr. Allen's corresponding functions.   This algorithm uses get(row, col) and set(row, col, val).   Mr. Allen's equivalent functions have col first and row second. If you find this algorithm useful, thank Gauss! // Reduce to complete row echelon form // By James D. Reilly, Fort Wayne, Indiana double Matrix::Reduce(void) {    int B, C, X;    double Pivot, Temp;    double Determinant;    int PivotRow, PivotCol;    PivotRow = 0;    PivotCol = 0;    Determinant = 1.0;    do    {       // Find largest pivot.   Search for a number below       // the current pivot with a greater absolute value.       X = PivotRow;       for(C=PivotRow; C<rows; C++)          if(fabs(Get(C, PivotCol))>fabs(Get(X, PivotCol)))             X = C;       if(X != PivotRow)       {          // If here, there is a better pivot choice somewhere          // below the current pivot.          // Interchange the pivot row with the row          // containing the largest pivot, X.          for(B=0; B<cols; B++)          {             Temp = Get(PivotRow, B);             Set(PivotRow, B, Get(X, B));             Set(X, B, Temp);          }          Determinant = -Determinant;       }       Pivot = Get(PivotRow, PivotCol);       Determinant = Pivot*Determinant;       if(Pivot!= 0.0)       {          // Introduce a '1' at the pivot point          for(B=0; B<cols; B++)             Set(PivotRow, B, Get(PivotRow, B)/Pivot);          for(B=0; B<rows; B++)          {             // Eliminate (make zero) all elements above             // and below the pivot.             // Skip over the pivot row when we come to it.             if(B != PivotRow)             {                Pivot = Get(B, PivotCol);                for(C=PivotRow; C<cols; C++)                   Set(B, C, Get(B,C)-Pivot*Get(PivotRow, C));             }          }          PivotRow++; // Next row       }       PivotCol++;   // Next column    }    while((PivotRow<rows)&&(PivotCol<cols)); // Reached an edge yet?    return Determinant; } J. Reilly Sign In·View Thread·PermaLink 5.00/5

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