Question

I have a method that takes a std::vector as one of its parameters. Is there a way I can initialize a matrix by assigning the std::vector to the matrix? Here’s what I tried to do below. Does anyone know how i can achieve assigning the vector (or even a pointer of doubles) to the matrix? Thanks in advance. Mike

void Foo(std::vector v)
{
    matrix<double> m(m, n, v);
    // work with matrix...
}

Answer 1

According to the boost matrix documentation, there are 3 constructors for the matrix class: empty, copy, and one taking two size_types for the number of rows and columns. Since boost doesn’t define it (probably because there are many ways to do it and not every class is gong to define a conversion into every other class) you are going to need to define the conversion.

Here’s an approach that I would use, but since there are multiple ways to do this and the question doesn’t specify how you want this done you may find a different approach more applicable to your situation.

void Foo(const std::vector<double> & v) {
   size_t m = ... // you need to specify
   size_t n = ... // you need to specify

   if(v.size() < m * n)   { // the vector size has to be bigger or equal than m * n
      // handle this situation
   }

   matrix<double> mat(m, n);
   for(size_t i=0; i<mat.size1(); i++) {
      for(size_t j=0; j<mat.size2(); j++) {
         mat(i,j) = v[i+j*mat.size1()];
      }
   }
}

A couple of notes about your provided code: std::vector needs a templated argument and you are declaring m as a matrix and an input argument to it’s constructor.