A very basic primer on matrices, in pdf format (see the online reading page if you need help with pdf documents).
This is a systematic and well-illustrated introduction to linux.
If you've never used shell scripting before, this primer on shell scripting or this tutorial would be a start.
For Matlab, you can look at tutorials and demos offered by Mathworks itself. This site also contains links to Matlab tutorials at some universities. You may want to start with the Getting Started section. The short introduction to Matlab for psychologists from the University of Nottingham is also useful.
The scripting language Python is increasingly becoming popular for its flexibility and simplicity. You could start with the Beginners' Guide.
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