I am working on Gait analysis. I need to do EMG signal processing and it looks like Matlab is a good option for that. But I have collected data through Vicon motion capture systems and is it possible for me to use that data in Matalab? I am sure that the file format is different.
Any suggestions?
It is possible: the resulting files with a Vicon system are .c3d.
You must first go to c3d.org that explains how to read and write C3D files in the MATLAB environments.
Then, either you export your .c3d files and import it in MATLAB or you can use the PECS plug-in in Nexus to carry out the processings in MATLAB as a background task and see the results directly in Nexus.
See http://www.c3d.org
You could give it a try with : http://kitchen.cs.cmu.edu/tools.php
It is possible: the resulting files with a Vicon system are .c3d.
You must first go to c3d.org that explains how to read and write C3D files in the MATLAB environments.
Then, either you export your .c3d files and import it in MATLAB or you can use the PECS plug-in in Nexus to carry out the processings in MATLAB as a background task and see the results directly in Nexus.
See http://www.c3d.org
As others have mentioned, if you can get your data into the C3D format, there are many options for processing the signal. A great software tool that you can use in Matlab for reading and working with C3D files is the BTK (http://code.google.com/p/b-tk/) which is an open source project with great support. I think BTK is a great choice but other options include the popular C3D server software (http://www.c3dserver.com/).
I do this process on a daily basis using Vicon's PECS pipeline. Although PECS is a separate license that you have to purchase from Vicon, it allows me to export the data from Vicon directly into the Matlab workspace, where I can operate on it immediately or just save the workspace as a .mat file. I have also tried using freely available C3D readers (C3DServer), but this process works much more smoothly for me.
In addition to Dr. Gouelle's and Dr. Conrad's responses, Vicon also has a data export function that allows ASCII export, and you can select whether you'd like to export analog, force-plate, and/or marker-trajectory data. This may not be the most efficient option, though, because you add more data hard-drive space for data that can be read directly from the c3d.
As mentioned by Dr. Jacobs, I export to ASCII format for post-processing. Though this may add a step to my data processing queue, I work at a primarily undergraduate institution and often have undergraduate and/or master's students in my laboratory. I find this added step protects my data from unwanted corruption when processed by those with limited knowledge of file format or software.
I would agree with Drs Jacobs and Powell. We have had issues with the c3d format that Vicon Nexus uses to export analog data. We have found that ASCII or CSV seem to be much more reliable, and they are easily handled by Matlab.
Also what kind of filtering or processing techniques you guys will suggest me to work with???? All i need to do is to quantify the muscle activation properties (already collected the emg data using Vicon) with respect to gaitcycle????? What i can generate in the Polygon now is nothing but the raw data!!!!!
If you use either ascii or c3d export, you would have to read the gait events (like foot strike, foot off etc.) from the events section, then convert them to the sample number using the analog sampling frequency. I suggest to use the b-tk and get the analog sampling frequency by using the matlab b-tk command btkGetAnalogFrequency. Other than that, the analog sampling frequency can be found in the header of the ascii file. It should be noted that the analog frequency is almost certainly different from the frame rate of the motion capturing.
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