HOW TO: How do I filter a vector input to read only numeric cells?

HOW TO: How do I filter a vector input to read only numeric cells?

Question

How do I extract only the numeric values from an input vector?

Answer

Use the COper::Cell(...) method to inspect each cell, and add the contents to your input variable only if the cell is numeric.

1. In the Function Wizard, set the type to be COper.
2. In your add-in function declare a local variable of type vector<T> to accept the input values.
3. Use COper::IsVector() to ensure that your input is a vector (or a single cell, which is the trivial case of a vector).
4. Call COper::GetVectorCount() to get the number of cells in the unfiltered vector.
5. Use COper::Cell(...) to inspect a cell directly.
6. Use COper::IsDouble() to test the contents of each cell.

The example functions below demonstrate this technique for a vector<double> argument.

Example

// Function:    FilterVec
// Purpose:     Extracts only the numeric values from a vector

//{{XLP_SRC(FilterVec)
    // NOTE - the FunctionWizard will add and remove mapping code here.
    //    DO NOT EDIT what you see in these blocks of generated code!
IMPLEMENT_XLLFN2(FilterVec, "RP", "FilterVec", "A", "User Defined"
    "", "Extracts only the numeric values from a vector", 
    "Vector containing values of various types\000", "\0appscope="
    "1\0", 1)

extern "C" __declspec( dllexport )
LPXLOPER FilterVec(const COper* A)
{
    XLL_FIX_STATE;
    CXlOper xloResult;
//}}XLP_SRC

    std::vector<double> vecA;
    if (A->IsVector())
    {
        for (USHORT i = 0; i < A->GetVectorCount(); i++)
            if (A->VectorCell(i).IsDouble())
                vecA.push_back(A->VectorCell(i).ToDouble());
        xloResult = vecA;
    }
    
    return xloResult.Ret();
}