How can I label a solution as NaN in a MEX code?

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AP
AP 2014-6-24
编辑： José-Luis 2014-6-24
I am using solvers of LAPACK libraries in a MATLAB MEX file for solving linear system of equations. For some of the cases, the system that I solve is singular. For example, the system is as follows for one of my cases:
A =
0.00000000 0.00000000 0.00000000
0.00000000 0.00000000 0.00000000
0.00000000 0.00000000 77.31867171
b:
-0.00000000 -0.00000000 -0.00000000
What would be the best approach to label this solution as NaN similar to MATLAB?

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采纳的回答

James Tursa
James Tursa 2014-6-24
Use the API function mxGetNaN:
http://www.mathworks.com/help/matlab/apiref/mxgetnan.html?searchHighlight=mxgetnan
E.g., to put a NaN value into a double for returning to the MATLAB workspace:
double d = mxGetNaN( );

更多回答（1 个）

José-Luis
José-Luis 2014-6-24
if (some_condition)
some_value = 0.0/0.0; %This will produce a NaN
end
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AP
AP 2014-6-24
编辑：AP 2014-6-24
Since I am writing a c++ code in MATLAB, I am trying to find a way to label the solution of a singular matrix to NaN in the c++ code. I am using LAPACK solvers to solve a linear system of equation. At some point the solution to this system fail and I want to be able to label this as NaN in my c++ code. Hope this clarifies my question.
José-Luis
José-Luis 2014-6-24
编辑：José-Luis 2014-6-24
double myNaN = 0.0/0.0;
will produce a NaN in C++. Alternatively, you could set it to some other value
double flag = numeric_limits<double>::max();
that you then change into NaN in Matlab.

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