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POReading data from matlab files into C
 

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    <p>I'm trying to learn how to use the C API to reading Matlab <code>.mat</code> files, but it's not working as I expected:</p> <p>I'd like to just open a very simple <code>.mat</code> file called <code>test.mat</code>, read a value from the file and store it in a C variable. I've created <code>test.mat</code> in Matlab using the following commands:</p> <pre><code>&gt; value = 3; &gt; save ("test.mat", "value") </code></pre> <p>Below is my C code, which doesn't even compile - the compiler doesn't seem to find the header files. See below the code for compiler output. What am I doing wrong here?</p> <p><strong>Code:</strong></p> <pre><code>#include &lt;stdlib.h&gt; #include &lt;stdio.h&gt; #include &lt;mat.h&gt; #include &lt;matrix.h&gt; int main(int argc, char *argv[]) { double value; MATFile *datafile; datafile = matOpen("test.mat", "r"); mxArray *mxValue; mxValue = matGetVariable(datafile, "value"); matClose(datafile); value = *mxGetPr(mxArray); mxFree(mxArray); printf("The value fetched from the .mat file was: %f", value); return 0; } </code></pre> <p><strong>Compiler output:</strong></p> <pre><code>$ make animate_shot cc -I/usr/local/MATLAB/R2011a/extern/include/ animate_shot.c -o animate_shot /tmp/cczrh1vT.o: In function `main': animate_shot.c:(.text+0x1a): undefined reference to `matOpen' animate_shot.c:(.text+0x2f): undefined reference to `matGetVariable' animate_shot.c:(.text+0x3f): undefined reference to `matClose' animate_shot.c:(.text+0x4b): undefined reference to `mxGetPr' animate_shot.c:(.text+0x5e): undefined reference to `mxFree' collect2: ld returned 1 exit status make: *** [animate_shot] Error 1 </code></pre> <p>(the -I flag is specified with the line <code>CPPFLAGS=-I/usr/local/MATLAB/R2011a/extern/include/</code> in my makefile, and I've verified that the directory exists and contains the header files <code>mat.h</code> and <code>matrix.h</code>).</p> <p><strong>UPDATE:</strong><br> I've found that the libraries I need to link in are <code>libmat.so</code> and <code>libmx.so</code> (according to <a href="http://www.mathworks.se/help/techdoc/matlab_external/f19027.html">this MathWorks help article</a>), residing in <code>/usr/local/MATLAB/R2011a/bin/glnxa64/</code> on my system. I've therefore updated my makefile to this:</p> <pre><code>CPPFLAGS =-I/usr/local/MATLAB/R2011a/extern/include/ LDFLAGS = -L/usr/local/MATLAB/R2011a/bin/glnxa64 -l mat -l mx </code></pre> <p>Now, running <code>make</code> gives the following command:</p> <pre><code>cc -I/usr/local/MATLAB/R2011a/extern/include/ -L/usr/local/MATLAB/R2011a/bin/glnxa64 -l mat -l mx animate_shot.c -o animate_shot </code></pre> <p>However, I still get the same errors. Any ideas?</p>
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