converting vector<vector<double>> to mwArray

Hello,

I am trying to pass a 2 dimensional vector (a matrix) in C++ to a C++ share library matlab function compiled by Matlab Compiler.

I am trying to convert this vector, for example myvect, to the mwArray type so that by matlab function can use it. The myvect has the following format in C++,

vector<vector<double>> myvect(2);
myvect[0].push_back(0.1);
myvect[0].push_back(0.2);
myvect[0].push_back(10);
myvect[0].push_back(20);

I am trying:

mwArray mymtrx(2, 2, mxDOUBLE_CLASS);
mymtrx.SetData(&mymtrx[0][0], 4);

But it does not work. The data in mymtrx is not the same as the data in myvect.

How can I convert myvectinto mwArray type?

Thank you

Answer 1

[Kaustubha Govind]

Did you have a typo calling SetData?

mwArray mymtrx(2, 2, mxDOUBLE_CLASS);
mymtrx.SetData(&myvect[0][0], 4);

[hnde]

Hello,

Sorry for the typo. I am doing:

mwArray mymtrx(2, 2, mxDOUBLE_CLASS);

mymtrx.SetData(&myvect[0][0], 4);

But no matter what data is in myvect, the result that gets printed on the command screen is this :

1.0e+303*

0.0000 -0.0000

0.0000 -2.6570

Is there anything else I can try?

Thank you very much.

[Kaustubha Govind]

I know that something like:

vector<double> myvect(2);

mymtrx.SetData(&myvect[0], 2);

works, because the address of the first element of a std::vector returns the address to the builtin-array represented internally. However, since you are using a vector of vectors, I'm not sure that there is the same guarantee. You might want to explore this kind of conversion for std::vectors before you try this. I'm pretty sure that the problem lies in using &myvect[0][0].

[hnde]

Thank you for your answer.

It is exactly as you said. It works for the vector<double> case, but not for the vector<vector<double>> case.

I am out of ideas on how to do this.

Thank you for all your help.

[Jonathan Ingber Katz]

As Kaustubha Govind said, this in the general case will not work for a vector of vectors. I believe the best way to do this is to recast your vector of vectors as a single vector.