A Fast Fourier Transform or FFT is an algorithm that samples a signal over space (period of time) and divides it into its frequency components. The FFT is a fast implementation of the DFT (discrete Fourier transform), computational complexity is reduced by applying the FFT algorithm to a signal.

The FFT can simply be used to characterise the magnitude and phase of a signal, or it can be used in combination with other operations to perform computations such as convolution and correlation.

## Calculating the FFT of any time domain history curve in OnScale Post-process GUI

- Open you
**"XX.flxhst"**data file which contains Time History Curve results from within**OnScale Post-processor GUI** - Click one time only on the
**"functimefunc_1"**time history curve (or any other curve) - Click on the
**"FFT Record"**function which then becomes activated - Double click on the
**"functimefunc_1.amp"**which then appears under Frequency History to display the amplitude of the Impedance curve

**Note:** To open 2 windows like in this pictures, you will need to click on "Configure the Viewport" and change the view display.