In MATLAB I have to pass cut-off frequency for designing a filter. But this Cut-off frequency is in radians-per-sample. How do I convert my analog Cut off frequency in $\textrm{Hz}$, into the required radians-per-sample for MATLAB?
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Problems like these are best attacked using some dimensional analysis:
$$f_{[\rm rad/samples]} = f_{[\rm cycles/sec]}\cdot \frac{\text{sec}}{\text{samples}}\cdot \frac{\text{rad}}{\text{cycle}}$$
$$f_{[\rm rad/samples]} = f_{[\rm cycles/sec]}\cdot \frac{2\pi}{f_s}$$
where $f_s$ is the sample rate in $\textrm{Hz}$.
