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set pm3d at s hidden3d depthorder unset hidden3d
unset surf
splot x*x+y*y linecolor rgb "black" linewidth 0.5
Interpolate
The option interpolate m,n will interpolate grid points into a ner mesh, and color each quadrangle appropriately. For data les, this will smoothen the color surface, and enhance spikes in a color surface. For functions, interpolation makes little sense, except to trade o precision for memory. It would usually make more sense to use samples and isosamples when working with functions. For positive m and n, each quadrangle or triangle is interpolated m-times and n-times in the respective direction. For negative m and n, the interpolation frequency is chosen so that there will be at least jmj and jnj points drawn; you can consider this as a special gridding function. Zeros, i.e. interpolate 0,0, will automatically choose an optimal number of interpolated surface points.
Deprecated options
There used to be an option ftransparentjsolidg to this command. Now you get the same e ect from set grid ffrontjlayerdefaultg, respectively.
The command set pm3d map is equivalent to set pm3d at b; set view map; set style data pm3d; set style func pm3d;. It is used for backwards compatibility, when set view map was not available. Take care that you properly use zrange and cbrange for input data point ltering and color range scaling, respectively; and also set (no)surface seems to have a (side?) e ect.
Palette
Palette is a color storage for use by pm3d, lled color contours or polygons, color histograms, color gradient background, and whatever it is or it will be implemented... Here it stands for a palette of smooth "continuous" colors or grays, but let's call it just a palette.
Color palettes require terminal entries for lled color polygons and palettes of smooth colors, are currently available for terminals listed in help for set pm3d. The range of color values are adjustable independently by set cbrange and set log cb. The whole color palette is visualized in the colorbox.
Syntax:
set palette set palette {
{gray | color }
{gamma <gamma> }
{rgbformulae <r>,<g>,<b>
| defined { ( <gray1> <color1> {, <grayN> <colorN>}... ) } | file '<filename>' {datafile-modifiers}
| functions <R>,<G>,<B>
}
{cubehelix {start <val>} {cycles <val>} {saturation <val>} }
{model { RGB | HSV | CMY | YIQ | XYZ } }
{positive | negative }
{nops_allcF | ps_allcF }
{maxcolors <maxcolors> }
}
show palette
show palette palette <n> {{float | int}} show palette gradient
show palette fit2rgbformulae show palette rgbformulae
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show colornames
set palette (i.e. without options) sets up the default values. Otherwise, the options can be given in any order. show palette shows the current palette properties.
show palette gradient displays the gradient de ning the palette (if appropriate). show palette rgbformulae prints the available xed gray {> color transformation formulae. show colornames prints the known color names.
show palette palette <n> prints to the screen or to the le given by set print a table of RGB triplets calculated for the current palette settings and a palette having <n> discrete colors. The default wide table can be limited to 3 columns of r,g,b oat values [0..1] or integer values [0..255] by options oat or int, respectively. This way, the current gnuplot color palette can be loaded into other imaging applications, for example Octave. Additionally to this textual list of RGB table, you can use the test palette command to plot the R,G,B pro les for the current palette.
The following options determine the coloring properties.
Figure using this palette can be gray or color. For instance, in pm3d color surfaces the gray of each small spot is obtained by mapping the averaged z-coordinate of the 4 corners of surface quadrangles into the range [min z,max z] providing range of grays [0:1]. This value can be used directly as the gray for gray maps. The color map requires a transformation gray {> (R,G,B), i.e. a mapping [0:1] {> ([0:1],[0:1],[0:1]).
Basically two di erent types of mappings can be used: Analytic formulae to convert gray to color, or discrete mapping tables which are interpolated. palette rgbformulae and palette functions use analytic formulae whereas palette de ned and palette le use interpolated tables. palette rgbformulae reduces the size of postscript output to a minimum.
The command show palette t2rgbformulae nds the best matching set palette rgbformulae for the current set palette. Naturally, it makes sense to use it for non-rgbformulae palettes. This command can be found useful mainly for external programs using the same rgbformulae de nition of palettes as gnuplot, like zimg (
http://zimg.sourceforge.net
).
set palette gray switches to a gray only palette. set palette rgbformulae, set palette de ned, set palette le and set palette functions switch to a color mapping. set palette color is an easy way to switch back from the gray palette to the last color mapping.
Automatic gamma correction via set palette gamma <gamma> can be done for gray maps (set palette gray) and for the cubehelix color palette schemes. Gamma = 1 produces a linear ramp of intensity. See test palette (p. 172).
Many terminals support only discrete number of colors (e.g. 256 colors in gif). After the default gnuplot linetype colors are allocated, the rest of the available colors are by default reserved for pm3d. Thus a multiplot using multiple palettes could fail because the rst palette has used all the available color positions. You can mitigate this limitation by using set palette maxcolors <N> with a reasonably small value of N. This option causes N discrete colors to be selected from a continuous palette sampled at equally spaced intervals. If you want unequal spacing of N discrete colors, use set palette de ned instead of a single continuous palette.
RGB color space might not be the most useful color space to work in. For that reason you may change the color space with model to one of RGB, HSV, CMY, YIQ and XYZ. Using color names for set palette de ned tables and a color space other than RGB will result in funny colors. All explanation have been written for RGB color space, so please note, that R can be H, C, Y, or X, depending on the actual color space (G and B accordingly).
All values for all color spaces are limited to [0,1].
RGB stands for Red, Green and Blue; CMY stands for Cyan, Magenta and Yellow; HSV stands for Hue, Saturation, and Value; YIQ is the color model used by the U.S. Commercial Color Television Broadcasting, it is basically an RGB recoding with downward compatibility for black and white television; XYZ are the three primary colors of the color model de ned by the 'Commission Internationale de l'Eclairage' (CIE). For more information on color models see:
gnuplot 4.6 |
139 |
http://en.wikipedia.org/wiki/Color space
Rgbformulae
For rgbformulae three suitable mapping functions have to be chosen. This is done via rgbformulae <r>,<g>,<b>. The available mapping functions are listed by show palette rgbformulae. Default is 7,5,15, some other examples are 3,11,6, 21,23,3 or 3,23,21. Negative numbers, like 3,-11,-6, mean inverted color (i.e. 1-gray passed into the formula, see also positive (p. 139) and negative (p. 139) options below).
Some nice schemes in RGB color space
7,5,15 |
... traditional pm3d (black-blue-red-yellow) |
3,11,6 |
... green-red-violet |
23,28,3 |
... ocean (green-blue-white); try also all other permutations |
21,22,23 |
... hot (black-red-yellow-white) |
30,31,32 |
... color printable on gray (black-blue-violet-yellow-white) |
33,13,10 |
... rainbow (blue-green-yellow-red) |
34,35,36 |
... AFM hot (black-red-yellow-white) |
A full color palette in HSV color space
3,2,2 ... red-yellow-green-cyan-blue-magenta-red
Please note that even if called rgbformulae the formulas might actually determine the <H>,<S>,<V> or <X>,<Y>,<Z> or ... color components as usual.
Use positive and negative to invert the gure colors.
Note that it is possible to nd a set of the best matching rgbformulae for any other color scheme by the command
show palette fit2rgbformulae
De ned
Gray-to-rgb mapping can be manually set by use of palette de ned: A color gradient is de ned and used to give the rgb values. Such a gradient is a piecewise linear mapping from gray values in [0,1] to the RGB space [0,1]x[0,1]x[0,1]. You must specify the gray values and the corresponding RGB values between which linear interpolation will be done.
Syntax:
set palette defined { ( <gray1> <color1> {, <grayN> <colorN>}... ) }
<grayX> are gray values which are mapped to [0,1] and <colorX> are the corresponding rgb colors. The color can be speci ed in three di erent ways:
<color> := { <r> <g> <b> | '<color-name>' | '#rrggbb' }
Either by three numbers (each in [0,1]) for red, green and blue, separated by whitespace, or the name of the color in quotes or X style color speci ers also in quotes. You may freely mix the three types in a gradient de nition, but the named color "red" will be something strange if RGB is not selected as color space. Use show colornames for a list of known color names.
Please note, that even if written as <r>, this might actually be the <H> component in HSV color space or <X> in CIE-XYZ space, or ... depending on the selected color model.
The <gray> values have to form an ascending sequence of real numbers; the sequence will be automatically rescaled to [0,1].
set palette de ned (without a gradient de nition in braces) switches to RGB color space and uses a preset full-spectrum color gradient. Use show palette gradient to display the gradient.
Examples:
To produce a gray palette (useless but instructive) use:
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set palette model RGB
set palette defined ( 0 "black", 1 "white" )
To produce a blue yellow red palette use (all equivalent):
set palette defined ( 0 "blue", 1 "yellow", 2 "red" ) set palette defined ( 0 0 0 1, 1 1 1 0, 2 1 0 0 )
set palette defined ( 0 "#0000ff", 1 "#ffff00", 2 "#ff0000" )
To produce some rainbow-like palette use:
set palette defined ( 0 "blue", 3 "green", 6 "yellow", 10 "red" )
Full color spectrum within HSV color space: set palette model HSV
set palette defined ( 0 0 1 1, 1 1 1 1 )
set palette defined ( 0 0 1 0, 1 0 1 1, 6 0.8333 1 1, 7 0.8333 0 1)
Approximate the default palette used by MATLAB:
set pal defined (1 '#00008f', 8 '#0000ff', 24 '#00ffff', \ 40 '#ffff00', 56 '#ff0000', 64 '#800000')
To produce a palette with only a few, equally-spaced colors: set palette model RGB maxcolors 4
set palette defined ( 0 "yellow", 1 "red" )
'Tra c light' palette (non-smooth color jumps at gray = 1/3 and 2/3).
set palette model RGB |
|
|
|
set palette defined (0 "dark-green", |
1 |
"green", \ |
|
1 |
"yellow", |
2 |
"dark-yellow", \ |
2 |
"red", |
3 |
"dark-red" ) |
Functions
Use set palette functions <Rexpr>, <Gexpr>, <Bexpr> to de ne three formulae for the R(gray), G(gray) and B(gray) mapping. The three formulae may depend on the variable gray which will take values in [0,1] and should also produce values in [0,1]. Please note that <Rexpr> might be a formula for the H-value if HSV color space has been chosen (same for all other formulae and color spaces).
Examples:
To produce a full color palette use:
set palette model HSV functions gray, 1, 1
A nice black to gold palette:
set palette model XYZ functions gray**0.35, gray**0.5, gray**0.8
A gamma-corrected black and white palette gamma = 2.2
color(gray) = gray**(1./gamma)
set palette model RGB functions color(gray), color(gray), color(gray)
Cubehelix
The "cubehelix" option de nes a family of palettes in which color (hue) varies along the standard color wheel while at the same time the net intensity increases monotonically as the gray value goes from 0 to 1.
D A Green (2011) http://arxiv.org/abs/1108.5083
start de nes the starting point along the color wheel in radians. cycles de nes how many color wheel cycles span the palette range. Larger values of saturation produce more saturated color; saturation > 1 may lead to clipping of the individual RGB components and to intensity becoming non-monotonic. The palette is also a ected by set palette gamma. The default values are
set palette cubehelix start 0.5 cycles -1.5 saturation 1 set palette gamma 1.5