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dpssload

Load discrete prolate spheroidal sequences from database

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Syntax

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

Description

[dpsSeq,lambda] = dpssload(seqLength,timeHalfBW) loads all sequences with length seqLength and time-bandwidth product timeHalfBW in the columns of dpsSeq and their corresponding concentrations in vector lambda from the DPSS MAT-file database dpss.mat. Create the dpss.mat file using dpsssave.

example

Examples

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Open Live Script

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

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Sequence length, specified as a positive integer.

Data Types: single | double

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

Data Types: single | double

Output Arguments

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Slepian sequences, returned as a matrix with a number of rows equal to seqLength and columns equal to round(2*timeHalfBW).

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

More About

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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

See Also

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