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#### A.4.4.7 Spectrogram Layer Control

This control is experimental. It is missing some important features, and the interface may be changed in a future version.

The Spectrogram Layer Control () plots a spectrum at successive (usually, but not necessarily, regularly-spaced) points in a time series. It is only available for the Time Plot Window.

Time Plot window with a Spectrogram layer

This control has only one layer-specific tab, Data, described below. The Zone tab is described in Appendix A.4.12.1.

Spectrogram control Data tab

The Data tab allows you to specify which values from a table will generate a spectrogram. It has the following fields:

Table
  The table supplying the data.
Time
  A table column or expression giving the epoch coordinate at which spectra are located. This should normally be a time-typed column; if it is simply of numeric type it will be interpreted as seconds since 1 Jan 1970.
Spectrum
  An array-valued table column giving the spectral data.
TimeWidth
  A table column or expression (variable or constant) giving the temporal coverage of a plotted spectrum. If not filled in, it is assumed to be the most common (median) difference between time points.
Row Subset
  The subset for which the spectrum should be plotted. To plot multiple subsets (not usually useful with this kind of plot) you would need multiple spectrogram layer controls in the stack.

To control the colour map used to represent the spectral values, use the Aux fixed control.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk