# dpssload

Load discrete prolate spheroidal sequences from database

## Description

## Examples

### Load Database of Slepian Sequences

The file `dpss.mat`

has four Slepian sequences. Each sequence has 128 samples and time-half-bandwidth product of 3, 6, 9, and 12. Load the sequence with a time-half-bandwidth product of 9.

seqLength = 128; timeHalfBW = 9; [dpsSeqRtrv,lambdaRtrv] = dpssload(seqLength,timeHalfBW);

List the variable information of the retrieved Slepian sequence and frequency-domain energy concentration ratios.

whos dpsSeqRtrv lambdaRtrv

Name Size Bytes Class Attributes dpsSeqRtrv 128x18 18432 double lambdaRtrv 18x1 144 double

## Input Arguments

`seqLength`

— Sequence length

positive integer

Sequence length, specified as a positive integer.

**Data Types: **`single`

| `double`

`timeHalfBW`

— Time-half-bandwidth product

positive scalar

Time-half-bandwidth product, specified as a positive scalar. This argument must be
less than `seqLength/2`

.

**Data Types: **`single`

| `double`

## Output Arguments

`dpsSeq`

— Slepian sequences

matrix

Slepian sequences, returned as a matrix with a number of rows equal to
`seqLength`

and columns equal to
`round(2*timeHalfBW)`

.

`lambda`

— Frequency-domain energy concentration ratios

column vector

Frequency-domain energy concentration ratios, returned as a column vector of length equal to the number of Slepian sequences.

## More About

### Structure of DPSS MAT- file Database

The `dpsssave`

function creates and stores a file named
`dpss.mat`

with the DPSS (Slepian sequences) that you generate with the
`dpss`

function.

The `dpsssave`

function assigns a location key (`1`

,
`2`

, …, `n`

) and a name (`E1`

,
`V1`

, `E2`

, `V2`

, ...,
`En`

, `Vn`

) for each Slepian sequence that it
generates and stores it in the `dpss.mat`

file, from the first to the
*n*th sequence.

A `dpss.mat`

file with *n* sequences presents the
following structure:

`E1`

,`E2`

, …,`En`

— Slepian sequences.`V1`

,`V2`

, …,`Vn`

— Frequency-domain energy concentration ratios.`index`

— Database index, a`struct`

array with information of the list of sequence lengths, time-half bandwidth products and locations of the Slepian sequences stored in the DPSS MAT-file database. This structure array comprises of the following fields:`N`

— Vector of sequence lengths. The`dpsssave`

function assigns a single entry in`N`

for each different value of sequence length.`Wlist`

— Structure array of time-half bandwidth products`NW`

and sequence location numbers`key`

. The`dpsssave`

function assigns a sequence location`key`

to each Slepian sequence each time you call it.

`next_key`

— Next-sequence identification key, defined as`next_key=n+1`

where`n`

is the number of Slepian sequences stored in the DPSS MAT-file database.

## Version History

**Introduced before R2006a**

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