# fold

Create one-sided spectrum amplitude vectors from the two-sided equivalents.

## Syntax

amp1 = fold(amp2)

amp1 = fold(amp2,dim)

## Inputs

amp2
Two-sided amplitudes.
Type: double
Dimension: vector | matrix
dim
Dimension on which to perform the calculation.
(default: first non-singular dimension).
Type: integer
Dimension: scalar

## Outputs

amp1
One-sided amplitudes.

## Examples

Examples with even number of inputs:

amp1 = fold([1,2,5,3,5,2])
amp1 = [Matrix] 1 x 4
1   4  10   3
Example with odd number of inputs:
amp1 = fold([1,2,5,3,3,5,2])
amp1 = [Matrix] 1 x 4
1   4  10   6

fold is only meaningful for symmetrical inputs, usually produced from real time domain signals. The positive half of the spectrum (below the Nyquist frequency) is doubled, thus effectively folding the spectrum in half.

freq with the 'onesided' option can be useful to create appropriate x-axis values.