I couldn't find this issue in the forums or in the bug reports, so please let me know if it is a known issue.

I have a dynamic vector, and I am trying to transpose it in place so that a row vector becomes a column vector and vice versa. From what I understand transposeInPlace should permanently alter the structure of the vector unlike transpose. Here is some example code to show the erroneous output I am seeing:

// try to transpose a vector
Eigen::VectorXi colVector(5);
colVector << 1, 2, 3, 4, 5;
std::cout << "col vector: " << std::endl;
std::cout << colVector << std::endl;
std::cout << "row vector: " << std::endl;
colVector.transposeInPlace();
std::cout << colVector << std::endl;
// matrix transpose
Eigen::MatrixXi beforeTranspose(3,2);
beforeTranspose << 1,2,3,4,5,6;
std::cout << "matrix before transpose: " << std::endl;
std::cout << beforeTranspose << std::endl;
beforeTranspose.transposeInPlace();
std::cout << "matrix after transpose: " << std::endl;
std::cout << beforeTranspose << std::endl;

Here's the console output for this section of code:
col vector:
1
2
3
4
5
row vector:
1
2
3
4
5
matrix before transpose:
1 2
3 4
5 6
matrix after transpose:
1 3 5
2 4 6

As you can see the transposeInPlace works for the dynamic matrix but not the dynamic vector.

I am using the stable release of Eigen 2.0.12. I am running the code in Microsoft Visual Studio 2008 version 9.0.30729.1 SP.

Please let me know if I am doing something wrong or if this is a legitimate bug.

Thanks.

You're doing something wrong: since colVector is of type Eigen::VectorXi, which means "column vector", it can't be transposed in-place, as that would amount to trying to fit a row-vector in a col-vector.

This is something that we actually can't check for sure at compile-time, because if your vector had length 1, that would be a valid operation (albeit a NOP). But since this operation is either illegal or a NOP, I'm OK to forbid it. Just don't have time, patches welcome

Thanks for the quick answer. I wasn't aware that Eigen::VectorXi was just a column vector. I assumed it could handle either column or row vectors. I suggest that this distinction be added to the tutorial pages in order to avoid future confusion.

Thanks.