contour
Plots position density contours. This provides another way (alongside the auto and density shading modes) to visualise the characteristics of overdense regions in a crowded plot. It's not very useful if you just have a few points.
The contours are currently drawn as pixels rather than lines so they don't look very beautify in exported vector output formats (PDF, PostScript). This may be improved in the future.
Usage Overview:
layerN=contour colorN=<rrggbb>|red|blue|... nlevelN=<int-value> smoothN=<pixels> scalingN=linear|log|equal zeroN=<number> <pos-coord-paramsN> 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
.
<pos-coord-paramsN>
give a position for each row of the input table.
Their form depends on the plot geometry,
i.e. which plotting command is used.
For a plane plot (plot2plane
)
the parameters would be
xN
and yN
.
The coordinate parameter values are in all cases strings
interpreted as numeric expressions based on column names.
These can be column names, fixed values or algebraic
expressions as described in Section 10.
colorN = <rrggbb>|red|blue|...
(Color)
The value may be a six-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 colors.
These are currently
red
, blue
, green
, grey
, magenta
, cyan
, orange
, pink
, yellow
, black
, white
.
[Default: ff0000
]
icmdN = <cmds>
(ProcessingStep[])
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)
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)
ifmtN
parameter.
istreamN = true|false
(Boolean)
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
]
nlevelN = <int-value>
(Integer)
[Default: 5
]
scalingN = linear|log|equal
(LevelMode)
The available options are:
linear
log
equal
[Default: linear
]
smoothN = <pixels>
(Integer)
[Default: 4
]
zeroN = <number>
(Double)
[Default: 0.0
]