dpssload

Load discrete prolate spheroidal sequences from database

Syntax

dpsSeq = dpssload(seqLength,timeHalfBW)

[dpsSeq,lambda] = dpssload(seqLength,timeHalfBW)

Description

dpsSeq = dpssload(seqLength,timeHalfBW) loads the discrete prolate spheroidal (DPSS) or Slepian sequences with length seqLength and time-bandwidth product timeHalfBW from the DPSS MAT file database dpss.mat. Each column of dpsSeq corresponds to a sequence. To create the dpss.mat file, use the dpsssave function.

[dpsSeq,lambda] = dpssload(seqLength,timeHalfBW) additionally loads the frequency-domain energy concentration ratios corresponding to the sequences.

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 nth 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