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SPSS® 12.0 Command Syntax Reference

SPSS® 12.0 Command Syntax Reference

SPSS® 12.0 Command Syntax Reference

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BY Keyword<br />

CROSS Subcommand<br />

SPECTRA 1529<br />

• The frequency (horizontal) axis on a plot BY FREQ is scaled from 0 to 0.5, expressing the<br />

frequency as a fraction of the length of the series.<br />

• The periodogram and estimated spectrum (vertical axis) are scaled in natural logs.<br />

The following plot keywords are available:<br />

P Periodogram. This is the default.<br />

S Spectral density estimate.<br />

K Squared coherency. Applies only to bivariate analyses.<br />

CS Cospectral density estimate. Applies only to bivariate analyses.<br />

QS Quadrature spectrum estimate. Applies only to bivariate analyses.<br />

PH Phase spectrum. Applies only to bivariate analyses.<br />

A Cross amplitude. Applies only to bivariate analyses.<br />

G Gain. Applies only to bivariate analyses.<br />

ALL All plots. For bivariate analyses, this includes all plots listed above. For univariate<br />

analyses, this includes the periodogram and the spectral density estimate.<br />

By default, SPECTRA displays both frequency and period plots. You can use BY to produce<br />

only frequency plots or only period plots.<br />

• BY FREQ indicates that all plots are plotted by frequency only. Plots by period are not produced.<br />

• BY PERIOD indicates that all plots are plotted by period only. Plots by frequency are not<br />

produced.<br />

Example<br />

SPECTRA SER01<br />

/PLOT=P S BY FREQ.<br />

• This command plots both the periodogram and the spectral density estimate for SER01.<br />

The plots are shown by frequency only.<br />

CROSS is used to specify bivariate spectral analysis.<br />

• When CROSS is specified, the first series named on the VARIABLES subcommand is the<br />

independent variable. All remaining variables are dependent.<br />

• Each series after the first is analyzed with the first series independently of other series<br />

named.<br />

• Univariate analysis of each series specified is still performed.

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