How to get Vector of Complex numbers from two vectors (real & imag)

Question

I have two vectors of floats and i want them to become one vector of Complex numbers. I'm stuck. I don't mind using iterators, but i am sure it'd be rediscovering the wheel i'm not informed about. Is my code leading me in the right direction?

typedef std::vector<float> CVFloat;
CVFloat vA, vB;
//fil vectors
typedef std::complex<CVFloat> myComplexVector;
myComplexVector* vA_Complex = new myComplexVector(vA, vB);

The code above is going through the compiler correctly, but when i want to get single numbers from myComplexVector using iterator i get error "Undefined symbol 'const_iterator'" (Borland C++)

myComplexVector::const_iterator it = vA_Complex->begin();

Solution 1

Here you are creating a "complex" object whose real and imaginary parts are vectors of floats.
Maybe what you actually want to do is creating a vector of complex objects whose real and imaginary parts are floats?

EDIT: myComplexVector is not a vector, is a complex. That's why a const_iterator for it is not defined.

Solution 2

You can create a general "zip" function taking iterators to both vectors, and a convertor functor and an output iterator:

template< typename at_It1, typename at_It2, typename at_Transform, typename at_Out >
void zip( at_It1 from1, const at_It1 to1, 
          at_It2 from2, const at_It2 to2,
          at_Transform  tranformer,
          at_Out& av_Out ) {
    while( from1 != to1 ) {
        av_Out = transformer( *from1, *from2 );
        ++av_Out; ++from1; ++from2;
    }
}

struct DoubleToComplex {
     complex<double> operator()( const double d1, const double d2 ) const {
         return complex<double>( d1, d2 );
     }
};



zip( vA.begin(), vA.end(),
     vB.begin(), vB.end(),
     DoubleToComplex(),
     std::back_inserter( vTarget ) );

And I wish there were such a function in the STL...

Solution 3

Whay not do it much much easier?

vector< complex<float> > result;
for( int i = 0; i < vA.size(); i++ ) {
    result.push_back( complex<float>( vA[i], vB[i] ) );
}

Solution 4

This doesn't make any sense:

typedef std::complex<CVFloat> myComplexVector;

surely you mean

typedef std::complex <float> ComplexFloat;
typedef std::vector <ComplexFloat> CFVector;

or something similar?

Once ou have it you can simply iterate over the float vectors (assuming they contain matching values) and add to your complex vector using push_back():

CFVector v;

for ( int i = 0; i < vA.size(); i++ ) {
  v.push_back( ComplexFloat( vA[i], vB[i] ) );
}

Solution 5

The easiest way is just write the loop

myComplexVector cv;
for(CVFloat::iterator it1=vA.begin(), end1=vA.end(), 
      it2=vB.begin(), end2=vB.end();
    it1!=end1 && it2 != end2; ++it1, ++it2)
  cv.push_back(std::complex(*it1, *it2));

Edit: ... and follow Neil's advice to declare myComplexVector type properly.

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Comments

[Moyshe]

Heh, you're right of course. It works perfectly, thank you:) Sometimes it's so easy to get lost with some fake ideas. It is part of bigger project. I optimize convultion and i have to use existing class of dft which holds real and imag vectors separately.

[Mykola Golubyev]

Why to declare simple pair as complex in the time where complex already defined with all necessary operators overloaded?

[sharptooth]

You mean the sdt::complex class? I just had no idea it exists before you asked.