C++ (Cpp) MAT::Row Examples

Programming Language: C++ (Cpp)

Class/Type: MAT

Method/Function: Row

Examples at hotexamples.com: 2

C++ mat row is a function from the OpenCV library that allows you to access a specific row of a matrix. This function returns a pointer to the first element of the specified row.

Example 1:

cv::Mat A = cv::Mat::ones(3, 3, CV_32FC1); // Create a 3x3 matrix with all values set to 1
float* row = A.ptr(1); // Pointer to the second row of matrix A

In this example, we create a 3x3 matrix filled with ones. We then use the `ptr` function to get a pointer to the second row of matrix A. This pointer can be used to access and modify the elements of that row.

Example 2:

cv::Mat A = cv::Mat::eye(4, 4, CV_32FC1); // Create a 4x4 identity matrix
for(int i = 0; i < A.rows; i++) {
    float* row = A.ptr(i); // Pointer to each row of matrix A
    for(int j = 0; j < A.cols; j++) {
        row[j] *= 2; // Multiply each element of the row by 2
    }
}

In this example, we create a 4x4 identity matrix using the `eye` function. We then use a nested for loop to iterate over each row and multiply each element of that row by 2. This example demonstrates how you can use the `ptr` function to access and modify the elements of a matrix row-by-row. C++ mat row is part of the OpenCV library.

C++ (Cpp) MAT::Row - 2 examples found. These are the top rated real world C++ (Cpp) examples of MAT::Row extracted from open source projects. You can rate examples to help us improve the quality of examples.

Frequently Used Methods

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dim(27)

size1(12)

size2(6)

NumRows(6)

CreateRotationMatrix(5)

GetValue(5)

block(4)

destructive_resize(3)

CreateIdentityMatrix(3)

RotateVector(3)

tpose(2)

push_back(2)

max(2)

begin1(2)

min(2)

resize(2)

Set(2)

Row(2)

row(2)

safe_invert(2)

GetRotation(2)

t(2)

end1(2)

reset(1)

gaussInt(1)

setComponent(1)

isContinuous(1)

identity(1)

Cast(1)

end2(1)

determinant(1)

create(1)

begin2(1)

apply(1)

SetValue(1)

SetDims(1)

Rows(1)

RangeMap(1)

Print(1)

NumCols(1)

Multiply(1)

Get(1)

DomainMap(1)

col(1)

Example #1

Show file

File: demo_stokes.cpp Project: mliertzer/ngsolve

  static void GenerateMatrix (const FEL & bfel, const MIP & mip,
			      MAT & mat, LocalHeap & lh)
  {
    // must get the right elements, otherwise an exception is thrown.

    const CompoundFiniteElement & cfel = 
      dynamic_cast<const CompoundFiniteElement&> (bfel);

    // a scalar H1 element
    const ScalarFiniteElement<2> & fel_u = 
      dynamic_cast<const ScalarFiniteElement<2>&> (cfel[0]);
    const ScalarFiniteElement<2> & fel_p = 
      dynamic_cast<const ScalarFiniteElement<2>&> (cfel[2]);
    
    int nd_u = fel_u.GetNDof();
    int nd_p = fel_p.GetNDof();
    
    // transformation of derivatives from reference element to general element:
    FlatMatrixFixWidth<2> gradu(nd_u, lh);
    fel_u.CalcMappedDShape (mip, gradu);

    // the shape functions of the pressure
    FlatVector<> vecp(nd_p, lh);
    fel_p.CalcShape (mip.IP(), vecp);

    mat = 0;

    // the first nd_u shape functions belong to u_x, the next nd_u belong to u_y:
    mat.Rows(0,2).Cols(cfel.GetRange(0)) = Trans (gradu);
    mat.Rows(2,4).Cols(cfel.GetRange(1)) = Trans (gradu);

    // ... and finally nd_p shape functions for the pressure:
    mat.Row(4).Range(cfel.GetRange(2)) = vecp;
  }

Example #2

Show file

File: demo_stokes.cpp Project: mliertzer/ngsolve

  static void GenerateMatrix (const FEL & bfel, const MIP & mip,
			      MAT & mat, LocalHeap & lh)
  {
    const CompoundFiniteElement & cfel = 
      dynamic_cast<const CompoundFiniteElement&> (bfel);
    const ScalarFiniteElement<2> & fel_u = 
      dynamic_cast<const ScalarFiniteElement<2>&> (cfel[0]);
    
    int nd_u = fel_u.GetNDof();

    FlatVector<> vecu(nd_u, lh);
    fel_u.CalcShape (mip.IP(), vecu);

    mat = 0;
    mat.Row(0).Range(cfel.GetRange(0)) = vecu;
    mat.Row(1).Range(cfel.GetRange(1)) = vecu;
  }