How do I convert a timeseries to a different frequency band?

1. How do you convert time data to frequency data?
2. How do you convert FFT to frequency?
3. Why do we convert from time to frequency domain?

How do you convert time data to frequency data?

To convert a time domain signal into frequency domain, one must use the Fourier transform to do so. MATLAB has a function fft which is a Fast Fourier Transform algorithm designed to implement the Fourier Transform on digital signals.

How do you convert FFT to frequency?

Your k^th FFT result's frequency is 2*pi*k/N.

Why do we convert from time to frequency domain?

For mathematical systems governed by linear differential equations, a very important class of systems with many real-world applications, converting the description of the system from the time domain to a frequency domain converts the differential equations to algebraic equations, which are much easier to solve.