Next Previous Up Contents
Next: function
Up: Layer Types
Previous: densogram

8.3.20 gaussian

Plots a best fit Gaussian to the histogram of a sample of data. In fact, all this plotter does is to calculate the mean and standard deviation of the sample, and plot the corresponding Gaussian curve. The mean and standard deviation values are reported by the plot.

The normalise config option, perhaps in conjunction with binsize, can be used to scale the height of the plotted curve in data units. In this case, binsize just describes the bar width of a notional histogram whose outline the plotted Gaussian should try to fit, and is only relevant for some of the normalisation options.

Usage Overview:

   layerN=gaussian colorN=<rrggbb>|red|blue|... showmeanN=true|false
                   thickN=<pixels> dashN=dot|dash|...|<a,b,...>
                   antialiasN=true|false
                   normaliseN=none|area|unit|maximum|height
                   binsizeN=+<width>|-<count> xN=<num-expr> weightN=<num-expr>
                   inN=<table> ifmtN=<in-format> istreamN=true|false
                   icmdN=<cmds>

All the parameters listed here affect only the relevant layer, identified by the suffix N.

Example:

   stilts plot2plane in=mgc_ok.fits x=mgc_dc_sb
                     layer1=histogram color1=green
                     layer2=gaussian color2=grey thick2=3
                     ymax=1200

antialiasN = true|false       (Boolean)
If true, plotted lines are drawn with antialising. Antialised lines look smoother, but may take perceptibly longer to draw. Only has any effect for bitmapped output formats.

[Default: false]

binsizeN = +<width>|-<count>       (BinSizer)
Configures the width of histogram bins. If the supplied string is a positive number, it is interpreted as a fixed width in the data coordinates of the X axis (if the X axis is logarithmic, the value is a fixed factor). If it is a negative number, then it will be interpreted as the approximate number of bins to display across the width of the plot (though an attempt is made to use only round numbers for bin widths).

When setting this value graphically, you can use either the slider to adjust the bin count or the numeric entry field to fix the bin width.

[Default: -30]

colorN = <rrggbb>|red|blue|...       (Color)
The color of plotted data, given by name or as a hexadecimal RGB value.

The standard plotting colour names are red, blue, green, grey, magenta, cyan, orange, pink, yellow, black, light_grey, white. However, many other common colour names (too many to list here) are also understood. The list currently contains those colour names understood by most web browsers, from AliceBlue to YellowGreen, listed e.g. in the Extended color keywords section of the CSS3 standard.

Alternatively, a six-digit hexadecimal number RRGGBB may be supplied, optionally prefixed by "#" or "0x", giving red, green and blue intensities, e.g. "ff00ff", "#ff00ff" or "0xff00ff" for magenta.

[Default: red]

dashN = dot|dash|...|<a,b,...>       (float[])
Determines the dash pattern of the line drawn. If null (the default), the line is solid.

Possible values for dashed lines are dot, dash, longdash, dotdash. You can alternatively supply a comma-separated list of on/off length values such as "4,2,8,2".

icmdN = <cmds>       (ProcessingStep[])
Specifies processing to be performed on the layer N input table as specified by parameter inN. The value of this parameter is one or more of the filter commands described in Section 6.1. If more than one is given, they must be separated by semicolon characters (";"). This parameter can be repeated multiple times on the same command line to build up a list of processing steps. The sequence of commands given in this way defines the processing pipeline which is performed on the table.

Commands may alteratively be supplied in an external file, by using the indirection character '@'. Thus a value of "@filename" causes the file filename to be read for a list of filter commands to execute. The commands in the file may be separated by newline characters and/or semicolons.

ifmtN = <in-format>       (String)
Specifies the format of the input table as specified by parameter inN. The known formats are listed in Section 5.2.1. This flag can be used if you know what format your table is in. If it has the special value (auto) (the default), then an attempt will be made to detect the format of the table automatically. This cannot always be done correctly however, in which case the program will exit with an error explaining which formats were attempted.

[Default: (auto)]

inN = <table>       (StarTable)
The location of the input table. This may take one of the following forms: In any case, compressed data in one of the supported compression formats (gzip, Unix compress or bzip2) will be decompressed transparently.
istreamN = true|false       (Boolean)
If set true, the input table specified by the inN parameter will be read as a stream. It is necessary to give the ifmtN parameter in this case. Depending on the required operations and processing mode, this may cause the read to fail (sometimes it is necessary to read the table more than once). It is not normally necessary to set this flag; in most cases the data will be streamed automatically if that is the best thing to do. However it can sometimes result in less resource usage when processing large files in certain formats (such as VOTable).

[Default: false]

normaliseN = none|area|unit|maximum|height       (Normalisation)
Defines how, if at all, the bars of histogram-like plots are normalised or otherwise scaled vertically.

When used in the time plot only, time-specific options like per_second and per_day are available.

The available options are:

[Default: none]

showmeanN = true|false       (Boolean)
If true, a line is drawn at the position of the calculated mean.

[Default: true]

thickN = <pixels>       (Integer)
Thickness of plotted line in pixels.

[Default: 1]

weightN = <num-expr>       (String)
Weighting of data points. If supplied, each point contributes a value to the histogram equal to the data value multiplied by this coordinate. If not supplied, the effect is the same as supplying a fixed value of one.

The value is a numeric algebraic expression based on column names as described in Section 10.

xN = <num-expr>       (String)
Horizontal coordinate.

The value is a numeric algebraic expression based on column names as described in Section 10.


Next Previous Up Contents
Next: function
Up: Layer Types
Previous: densogram

STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk