density
Paints markers using a configurable colour map to indicate how many points are plotted over each other. Specifically, it colours each pixel according to how many times that pixel has has been covered by one of the markers plotted by the layer in question. To put it another way, it generates a false-colour density map with pixel granularity using a smoothing kernel of the form of the markers plotted by the layer. The upshot is that you can see the plot density of points or other markers plotted.
This is like auto mode, but with more user-configurable options.
Usage:
shadingN=density colorN=<rrggbb>|red|blue|... densemapN=blacker|whiter|inferno|... denseclipN=<lo>,<hi> denseflipN=true|false densequantN=<number> densefuncN=log|linear|sqrt|square densesubN=<lo>,<hi>
All the parameters listed here
affect only the relevant layer,
identified by the suffix
N
.
Associated parameters are as follows:
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
, light_grey
, white
.
[Default: red
]
denseclipN = <lo>,<hi>
(Subrange)
If the full range 0,1
is used,
the whole range of colours specified by the selected
shader will be used.
But if for instance a value of 0,0.5
is given,
only those colours at the left hand end of the ramp
will be seen.
If the null (default) value is chosen,
a default clip will be used.
This generally covers most or all of the range 0-1
but for colour maps which fade to white,
a small proportion of the lower end may be excluded,
to ensure that all the colours are visually distinguishable
from a white background.
This default is usually a good idea if the colour map
is being used with something like a scatter plot,
where markers are plotted against a white background.
However, for something like a density map when the whole
plotting area is tiled with colours from the map,
it may be better to supply the whole range
0,1
explicitly.
denseflipN = true|false
(Boolean)
[Default: false
]
densefuncN = log|linear|sqrt|square
(Scaling)
The available options are:
log
: Logarithmic scalinglinear
: Linear scalingsqrt
: Square root scalingsquare
: Square scaling[Default: log
]
densemapN = blacker|whiter|inferno|...
(Shader)
A mixed bag of colour ramps are available:
blacker
,
whiter
,
inferno
,
magma
,
plasma
,
viridis
,
cubehelix
,
sron
,
rainbow
,
rainbow2
,
rainbow3
,
pastel
,
accent
,
gnuplot
,
gnuplot2
,
specxby
,
set1
,
paired
,
hotcold
,
rdbu
,
piyg
,
brbg
,
cyan-magenta
,
red-blue
,
brg
,
heat
,
cold
,
light
,
greyscale
,
colour
,
standard
,
bugn
,
bupu
,
orrd
,
pubu
,
purd
,
huecl
,
hue
,
intensity
,
rgb_red
,
rgb_green
,
rgb_blue
,
hsv_h
,
hsv_s
,
hsv_v
,
yuv_y
,
yuv_u
,
yuv_v
,
scale_hsv_s
,
scale_hsv_v
,
scale_yuv_y
.
Note:
many of these, including rainbow-like ones,
are frowned upon by the visualisation community.
[Default: blacker
]
densequantN = <number>
(Double)
If left blank, the colour map is nominally continuous (though in practice it may be quantised to a medium-sized number like 256).
densesubN = <lo>,<hi>
(Subrange)
The default value "0,1
" therefore has
no effect.
The range could be restricted to its lower half
with the value 0,0.5
.
[Default: 0,1
]