# blockfftimag

The imaginary component of a Fast Fourier Transform (FFT) calculated using blocking.

## Syntax

blockfftimag(vec_expr, block_size, overlap)

## Argument

vec_expr
A valid vector expression.
block_size
The number of elements to be used for each FFT (should be a power of 2).
overlap
The number of elements shared between consecutive blocks.

## Example

Templex Expression Result
{blockfftimag(c1.y, 256, 128)} A vector is generated which is the imaginary component of the FFT of a vector c1.y, using a block size of 256 and an overlap of 128.
Curve Math Vectors Result
x = freq(c1.x[0:255:1])

y = blockfftimag(c1.y, 256, 128)

Given c1, a curve is created which is the imaginary component of the FFT of c1, using a block size of 256 and an overlap of 128.

## Comments

The blockfftimag function uses blocking to calculate the imaginary component of a Fast Fourier Transform (FFT). The FFT is complex-valued and used to map time-domain data into the frequency domain. vec_expr is assumed to be evenly sampled. The resultant vector has a number of elements equal to the least power of two greater than or equal to block_size.

The blockfftimag function is different from a normal FFT in that it introduces blocking. The input vector is subdivided into blocks, each having block_size number of elements. An FFT is then performed on each individual block. The results of these FFTs are then averaged to give the final result.