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Reading C3D files through Matlab

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Example code for using the C3DFileAdapter in C++ is found below. This code is part of a test script that runs the C3D reader and checks for correct values. 

Converting Force, COP, and NaNs

When computing Center of Pressure (COP), often the numerical value will be computed as NaN (Not A Number). NaN values occur when the force values become zero. Typically, most COP computation systems include some cut-off value that zeros all forces below a threshold, which stops these NaNs from occurring. OpenSim does not do any processing of your force or COP and so when converting your C3D files to mot files, you may encounter NaN values. This is problematic during Inverse Dynamics analysis as you will get all NaN values for the output moments. This is because OpenSim splines the force and COP data before computing joint moments and don't know how to deal with NaN values. If you find that your mot files are containing NaNs for COPs after conversion, you don't necessarily have to perform additional computations to remove the NaNs. The C3DFileAdapter includes an input parameter that determines how the forces are represented, so you can use the appropriate input parameter to have the forces and moments represented at the origin of the plate, rather than as a COP. This negates any chance for NaNs being included in your forces. 

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