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### B.16.1 Usage

The usage of `plothist` is

       stilts <stilts-flags> plothist xpix=<int-value> ypix=<int-value>
                                      font=dialog|serif|... fontsize=<int-value>
                                      fontstyle=plain|bold|italic|bold-italic
                                      legend=true|false title=<value>
                                      omode=swing|out|cgi|discard|auto
                                      out=<out-file>
                                      ofmt=png|png-transp|gif|jpeg|pdf|svg|eps|eps-gzip
                                      inN=<table> ifmtN=<in-format>
                                      istreamN=true|false cmdN=<cmds>
                                      xdataN=<expr> xlo=<float-value>
                                      xhi=<float-value> xlog=true|false
                                      xflip=true|false xlabel=<value>
                                      subsetNS=<expr> nameNS=<value>
                                      colourNS=<rrggbb>|red|blue|...
                                      barstyleNS=fill|open|...
                                      linewidthNS=<int-value>
                                      dashNS=dot|dash|...|<a,b,...>
                                      grid=true|false antialias=true|false
                                      sequence=<suffix>,<suffix>,...
                                      ylo=<float-value> yhi=<float-value>
                                      ylog=true|false ylabel=<value>
                                      weightN=<value> binwidth=<float-value>
                                      norm=true|false cumulative=true|false
                                      binbase=<float-value>

If you don't have the `stilts` script installed, write "`java -jar stilts.jar`" instead of "`stilts`" - see Section 3. The available `<stilts-flags>` are listed in Section 2.1. For programmatic invocation, the Task class for this command is `uk.ac.starlink.ttools.task.TableHistogram`.

Parameter values are assigned on the command line as explained in Section 2.3. They are as follows:

`antialias = true|false` (Boolean)
  Controls whether lines are drawn using antialiasing, where applicable. If lines are drawn to a bitmapped-type graphics output format setting this parameter to true smooths the lines out by using gradations of colour for diagonal lines, and setting it false simply sets each pixel in the line to on or off. For vector-type graphics output formats, or for cases in which no diagonal lines are drawn, the setting of this parameter has no effect. Setting it true may slow the plot down slightly.

  [Default: `true`]

`barstyleNS = fill|open|...` (BarShape)
  Defines how histogram bars will be drawn for dataset NS. The options are:
  - `fill`
  - `open`
  - `tops`
  - `semi`
  - `semitops`
  - `spikes`
  - `fillover`
  - `openover`

  [Default: `fill`]

`binbase = <float-value>` (Double)
  Adjusts the offset of the bins. By default zero (or one for logarithmic X axis) is a boundary between bins; other boundaries are defined by this and the bin width. If this value is adjusted, the lower bound of one of the bins will be set to this value, so all the bins move along by the corresponding distance.

  [Default: `0.0`]

`binwidth = <float-value>` (Double)
  Defines the width on the X axis of histogram bins. If the X axis is logarithmic, then this is a multiplicative value.
`cmdN = <cmds>` (ProcessingStep[])
  Specifies processing to be performed on the table. 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, and lines which are blank or which start with a '`#`' character are ignored.

`colourNS = <rrggbb>|red|blue|...` (Color)
  Defines the colour of bars plotted for data set NS. The value may be a 6-digit hexadecimal number giving red, green and blue intensities, e.g. "`ff00ff`" for magenta. Alternatively it may be the name of one of the pre-defined colours. These are currently red, blue, green, grey, magenta, cyan, orange, pink, yellow, black and white.

  For most purposes, either the American or the British spelling is accepted for this parameter name.

`cumulative = true|false` (Boolean)
  Determines whether historams are cumulative. When false (the default), the height of each bar is determined by counting the number of points which fall into the range on the X axis that it covers. When true, the height is determined by counting all the points between negative infinity and the upper bound of the range on the X axis that it covers.

  [Default: `false`]

`dashNS = dot|dash|...|<a,b,...>` (float[])
  Defines the dashing pattern for lines drawn for dataset NS. To generate a dashed line the value may be one of the named dash types:
  - `dot`
  - `dash`
  - `longdash`
  - `dotdash`
  or may be a comma-separated string of on/off length values such as "`4,2,8,2`". A `null` value indicates a solid line. Only certain bar styles are affected by the dash pattern.
`font = dialog|serif|...` (String)
  Determines the font that will be used for textual annotation of the plot, including axes etc. At least the following fonts will be available:
  - `serif`
  - `sansserif`
  - `monospaced`
  - `dialog`
  - `dialoginput`
  as well as a range of system-dependent fonts, possibly including
  - `aakar`
  - `abyssinica_sil`
  - `ani`
  - `anjalioldlipi`
  - `bitstream_charter`
  - `c059`
  - `century_schoolbook_l`
  - `chandas`
  - `chilanka`
  - `courier`
  - `courier_10_pitch`
  - `d050000l`
  - `dejavu_sans`
  - `dejavu_sans_mono`
  - `dejavu_serif`
  - `dingbats`
  - `droid_sans_fallback`
  - `dyuthi`
  - `freemono`
  - `freesans`
  - `freeserif`
  - `gargi`
  - `garuda`
  - `gayathri`
  - `...`

  [Default: `dialog`]

`fontsize = <int-value>` (Integer)
  Sets the font size used for plot annotations.

  [Default: `12`]

`fontstyle = plain|bold|italic|bold-italic` (Integer)
  Gives a style in which the font is to be applied for plot annotations. Options are `plain`, `bold`, `italic` and `bold-italic`.

  [Default: `plain`]

`grid = true|false` (Boolean)
  If true, grid lines are drawn on the plot. If false, they are absent.

  [Default: `true`]

`ifmtN = <in-format>` (String)
  Specifies the format of the input table as specified by parameter `inN`. The known formats are listed in Section 5.1.1. 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. This parameter is ignored for scheme-specified tables.

  [Default: `(auto)`]

`inN = <table>` (StarTable)
  The location of the input table. This may take one of the following forms:
  - A filename.
  - A URL.
  - The special value "`-`", meaning standard input. In this case the input format must be given explicitly using the `ifmtN` parameter. Note that not all formats can be streamed in this way.
  - A scheme specification of the form `:<scheme-name>:<scheme-args>`.
  - A system command line with either a "`<`" character at the start, or a "`|`" character at the end ("`<syscmd`" or "`syscmd|`"). This executes the given pipeline and reads from its standard output. This will probably only work on unix-like systems.
  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). This parameter is ignored for scheme-specified tables.

  [Default: `false`]

`legend = true|false` (Boolean)
  Determines whether a legend showing which plotting style is used for each data set. Defaults to true if there is more than one set, false otherwise.
`linewidthNS = <int-value>` (Integer)
  Defines the line width for lines drawn as part of the bars for dataset NS. Only certain bar styles are affected by the line width.

  [Default: `2`]

`nameNS = <value>` (String)
  Provides a name to use for a subset with the symbolic label NS. This name will be used for display in the legend, if one is displayed.
`norm = true|false` (Boolean)
  Determines whether bin counts are normalised. If true, histogram bars are scaled such that summed height of all bars over the whole dataset is equal to one. Otherwise (the default), no scaling is done.

  [Default: `false`]

`ofmt = png|png-transp|gif|jpeg|pdf|svg|eps|eps-gzip` (GraphicExporter)
  Graphics format in which the plot is written to the output file, see Section 8.6. One of:
  - `png`: PNG
  - `png-transp`: PNG with transparent background
  - `gif`: GIF
  - `jpeg`: JPEG
  - `pdf`: Portable Document Format
  - `svg`: Scalable Vector Graphics
  - `eps`: Encapsulated PostScript
  - `eps-gzip`: Gzipped Encapsulated PostScript
  May default to a sensible value depending on the filename given by `out`.
`omode = swing|out|cgi|discard|auto` (PaintMode)
  Determines how the drawn plot will be output, see Section 8.5.
  - `swing`: Plot will be displayed in a window on the screen. This plot is "live"; it can be resized and (except for old-style plots) navigated around with mouse actions in the same way as plots in TOPCAT.
  - `out`: Plot will be written to a file given by `out` using the graphics format given by `ofmt`.
  - `cgi`: Plot will be written in a way suitable for CGI use direct from a web server. The output is in the graphics format given by `ofmt`, preceded by a suitable "Content-type" declaration.
  - `discard`: Plot is drawn, but discarded. There is no output.
  - `auto`: Behaves as `swing` or `out` mode depending on presence of `out` parameter

  [Default: `auto`]

`out = <out-file>` (uk.ac.starlink.util.Destination)
  The location of the output file. This is usually a filename to write to. If it is equal to the special value "-" the output will be written to standard output.
`sequence = <suffix>,<suffix>,...` (String[])
  Can be used to control the sequence in which different datasets and subsets are plotted. This will affect which symbols are plotted on top of, and so potentially obscure, which other ones. The value of this parameter is a comma-separated list of the "`NS`" suffixes which appear on the parameters which apply to subsets. The sets which are named will be plotted in order, so the first-named one will be at the bottom (most likely to be obscured). Note that if this parameter is supplied, then only those sets which are named will be plotted, so this parameter may also be used to restrict which plots appear (though it may not be the most efficient way of doing this). If no explicit value is supplied for this parameter, sets will be plotted in some sequence decided by STILTS (probably alphabetic by suffix).
`subsetNS = <expr>` (String)
  Gives the selection criterion for the subset labelled "`NS`". This is a boolean expression which may be the name of a boolean-valued column or any other boolean-valued expression. Rows for which the expression evaluates true will be included in the subset, and those for which it evaluates false will not.
`title = <value>` (String)
  A one-line title to display at the top of the plot.
`weightN = <value>` (String)
  Defines a weighting for each point accumulated to determine the height of plotted bars. If this parameter has a value other than 1 (the default) then instead of simply accumulating the number of points per bin to determine bar height, the bar height will be the sum over the weighting expression for the points in each bin. Note that with weighting, the figure drawn is no longer strictly speaking a histogram.

  When weighted, bars can be of negative height. An anomaly of the plot as currently implemented is that the Y axis never descends below zero, so any such bars are currently invisible. This may be amended in a future release (contact the author to lobby for such an amendment).

  [Default: `1`]

`xdataN = <expr>` (String)
  Gives a column name or expression for the x axis data for table N. The expression is a numeric algebraic expression based on column names as described in Section 10
`xflip = true|false` (Boolean)
  If set true, the scale on the x axis will increase in the opposite sense from usual (e.g. right to left rather than left to right).

  [Default: `false`]

`xhi = <float-value>` (Double)
  The upper limit for the plotted x axis. If not set, a value will be chosen which is high enough to accommodate all the data.
`xlabel = <value>` (String)
  Specifies a label to be used for annotating axis x. A default values based on the plotted data will be used if no value is supplied for this parameter.
`xlo = <float-value>` (Double)
  The lower limit for the plotted x axis. If not set, a value will be chosen which is low enough to accommodate all the data.
`xlog = true|false` (Boolean)
  If false (the default), the scale on the x axis is linear; if true it is logarithmic.

  [Default: `false`]

`xpix = <int-value>` (Integer)
  The width of the output graphic in pixels.

  [Default: `400`]

`yhi = <float-value>` (Double)
  Upper bound for Y axis. Autogenerated from the data if not supplied.
`ylabel = <value>` (String)
  Specifies a label for annotating the vertical axis. A default value based on the type of histogram will be used if no value is supplied for this parameter.

  [Default: `Count`]

`ylo = <float-value>` (Double)
  Lower bound for Y axis.

  [Default: `0.0`]

`ylog = true|false` (Boolean)
  Whether to use a logarithmic scale for the Y axis.

  [Default: `false`]

`ypix = <int-value>` (Integer)
  The height of the output graphic in pixels.

  [Default: `300`]

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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