dpssclear

Remove discrete prolate spheroidal sequences from database

Syntax

dpssclear(seqLength,timeHalfBW)

Description

dpssclear(seqLength,timeHalfBW) removes sequences with length seqLength and time-half-bandwidth product timeHalfBW from the DPSS MAT file database dpss.mat. Create the dpss.mat file using dpsssave.

Examples

Clear Database of Slepian Sequences

Generate four Slepian sequences. Each sequence has 128 sequences and time-half-bandwidth product of 3, 6, 9, and 12.

sL = [128 128 128 128]; % Segment length
tHBW = [3 6 9 12]; % Time-half-bandwidth product
for k=1:length(sL)
    [dpsSeq,lambda] = dpss(sL(k),tHBW(k));
    dpsssave(tHBW(k),dpsSeq,lambda);
end

Clear the sequence with a time-half-bandwidth product of 6.

seqLength = 128;
timeHalfBW = 6;

dpssclear(seqLength,timeHalfBW);

List the variable information of the modified Slepian sequence database file. The second sequence is empty.

whos -file dpss.mat

  Name            Size            Bytes  Class     Attributes

  E1            128x6              6144  double              
  E2              0x0                 0  double              
  E3            128x18            18432  double              
  E4            128x24            24576  double              
  V1              6x1                48  double              
  V2              0x0                 0  double              
  V3             18x1               144  double              
  V4             24x1               192  double              
  index           1x1              1091  struct              
  next_key        1x1                 8  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

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