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82 gnuplot 4.0 36 SET-SHOW trange, urange, and vrange. These ranges may be set directly with set trange, set urange, and set vrange, or by specifying the range on the plot or splot commands. Currently the default range for these parametric variables is [-5:5]. Setting the ranges to something more meaningful is expected. 36.47 Plot The show plot command shows the current plotting command as it results from the last plot and/or splot and possible subsequent replot commands. In addition, the show plot add2history command adds this current plot command into the history. It is useful if you have used replot to add more curves to the current plot and you want to edit the whole command now. 36.48 Pm3d pm3d is an splot style for drawing palette-mapped 3d and 4d data as color/gray maps and surfaces. It uses a pm3d algorithm which allows plotting gridded as well as non-gridded data without preprocessing, even when the data scans do not have the same number of points. Drawing of color surfaces is available on terminals supporting filled colored polygons with color mapping specified by palette. Currently supported terminals include Screen terminals: OS/2 Presentation Manager X11 Linux VGA (vgagl) GGI Windows AquaTerm (Mac OS X) Files: PostScript pslatex, pstex, epslatex gif, png, jpeg (x)fig tgif cgm pdf svg Let us first describe how a map/surface is drawn. The input data come from an evaluated function or from an splot data file. Each surface consists of a sequence of separate scans (isolines). The pm3d algorithm fills the region between two neighbouring points in one scan with another two points in the next scan by a gray (or color) according to z-values (or according to an additional ’color’ column, see help for using (p. 43)) of these 4 corners; by default the 4 corner values are averaged, but this can be changed by the option corners2color. In order to get a reasonable surface, the neighbouring scans should not cross and the number of points in the neighbouring scans should not differ too much; of course, the best plot is with scans having same number of points. There are no other requirements (e.g. the data need not be gridded). Another advantage is that the pm3d algorithm does not draw anything outside of the input (measured or calculated) region. Surface coloring works with the following input data: 1. splot of function or of data file with one or three data columns: The gray/color scale is obtained by mapping the averaged (or corners2color) z-coordinate of the four corners of the above-specified quadrangle into the range [min color z,max color z] of zrange or cbrange providing a gray value in the range [0:1]. This value can be used directly as the gray for gray maps. The normalized gray value can be further mapped into a color — see set palette (p. 85) for the complete description. 2. splot of data file with two or four data columns: The gray/color value is obtained by using the last-column coordinate instead of the z-value, thus allowing the color and the z-coordinate be mutually
36 SET-SHOW gnuplot 4.0 83 independent. This can be used for 4d data drawing. Other notes: 1. The term ’scan’ referenced above is used more among physicists than the term ’iso curve’ referenced in gnuplot documentation and sources. You measure maps recorded one scan after another scan, that’s why. 2. The ’gray’ or ’color’ scale is a linear mapping of a continuous variable onto a smoothly varying palette of colors. The mapping is shown in a rectangle next to the main plot. This documentation refers to this as a "colorbox", and refers to the indexing variable as lying on the colorbox axis. See set colorbox (p. 60), set cbrange (p. 154). 3. To use pm3d coloring to generate a two-dimensional plot rather than a 3D surface, use set view map or set pm3d map. Syntax: set pm3d set pm3d { } show pm3d unset pm3d { at } { scansautomatic | scansforward | scansbackward } { flush { begin | center | end } } { ftriangles | noftriangles } { clip1in | clip4in } { corners2color { mean|geomean|median|c1|c2|c3|c4 } } { hidden3d | nohidden3d } { implicit | explicit } { map } Setting set pm3d (i.e. without options) sets up the default values. Otherwise, the options can be given in any order. Color surface can be drawn at the base or top (then it is a gray/color planar map) or at z-coordinates of surface points (gray/color surface). This is defined by the at option with a string of up to 6 combinations of b, t and s. For instance, at b plots at bottom only, at st plots firstly surface and then top map, while at bstbst will never by seriously used. Colored quadrangles are plotted one after another. When plotting surfaces (at s), the later quadrangles overlap (overdraw) the previous ones. (Gnuplot is not virtual reality tool to calculate intersections of filled polygon meshes.) You may try to switch between scansforward and scansbackward to force the first scan of the data to be plotted first or last. The default is scansautomatic where gnuplot makes a guess about scans order. If two subsequent scans do not have same number of points, then it has to be decided whether to start taking points for quadrangles from the beginning of both scans (flush begin), from their ends (flush end) or to center them (flush center). Note, that flush (center|end) are incompatible with scansautomatic: if you specify flush center or flush end and scansautomatic is set, it is silently switched to scansforward. If two subsequent scans do not have the same number of points, the option ftriangles specifies whether color triangles are drawn at the scan tail(s) where there are not enough points in either of the scan. This can be used to draw a smooth map boundary. Clipping with respect to x, y coordinates of quadrangles can be done in two ways. clip1in: all 4 points of each quadrangle must be defined and at least 1 point of the quadrangle must lie in the x and y ranges. clip4in: all 4 points of each quadrangle must lie in the x and y ranges. There is a single gray/color value associated to each drawn pm3d quadrangle (no smooth color change among vertices). The value is calculated from z-coordinates from the surrounding corners according to corners2color . The options ’mean’ (default), ’geomean’ and ’median’ produce various kinds of surface color smoothing. This may not be desired for pixel images or for maps with sharp and intense peaks, in which case the options ’c1’, ’c2’, ’c3’ or ’c4’ can be used instead to assign the
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gnuplot An Interactive Plotting Pro
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CONTENTS gnuplot 4.0 3 12.1 Bind .
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CONTENTS gnuplot 4.0 5 36.9 Clip .
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CONTENTS gnuplot 4.0 7 36.57.6.18 Y
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CONTENTS gnuplot 4.0 9 36.59.62 Svg
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CONTENTS gnuplot 4.0 11 36.114Cbtic
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3 SEEKING-ASSISTANCE gnuplot 4.0 13
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4 WHAT IS NEW IN VERSION 4.0 gnuplo
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6 COMMAND-LINE-EDITING gnuplot 4.0
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10 EXPRESSIONS gnuplot 4.0 19 FIT S
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10 EXPRESSIONS gnuplot 4.0 21 other
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11 GLOSSARY gnuplot 4.0 23 10.3 Use
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13 PLOTTING gnuplot 4.0 25 ctrl, al
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17 TIME/DATE DATA gnuplot 4.0 27 co
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21 EXIT gnuplot 4.0 29 19 Call The
Page 31 and 32: 22 FIT gnuplot 4.0 31 current param
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Page 35 and 36: 22 FIT gnuplot 4.0 35 (branch) for
Page 37 and 38: 26 LOAD gnuplot 4.0 37 if () [; el
Page 39 and 40: 28 PLOT gnuplot 4.0 39 28.1 Data-fi
Page 41 and 42: 28 PLOT gnuplot 4.0 41 28.1.4 Smoot
Page 43 and 44: 28 PLOT gnuplot 4.0 43 pop(x) = 103
Page 45 and 46: 28 PLOT gnuplot 4.0 45 (x, y, ydelt
Page 47 and 48: 28 PLOT gnuplot 4.0 47 This is the
Page 49 and 50: 31 QUIT gnuplot 4.0 49 This plots "
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Page 67 and 68: 36 SET-SHOW gnuplot 4.0 67 Tic-mark
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Page 93 and 94: 36 SET-SHOW gnuplot 4.0 93 Examples
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Page 97 and 98: 36 SET-SHOW gnuplot 4.0 97 36.57.6.
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36 SET-SHOW gnuplot 4.0 133 set ori
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36 SET-SHOW gnuplot 4.0 135 The cha
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36 SET-SHOW gnuplot 4.0 137 System
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36 SET-SHOW gnuplot 4.0 139 or [no]
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36 SET-SHOW gnuplot 4.0 141 gnuplot
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36 SET-SHOW gnuplot 4.0 143 36.62 T
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36 SET-SHOW gnuplot 4.0 145 36.68 U
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36 SET-SHOW gnuplot 4.0 147 See als
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36 SET-SHOW gnuplot 4.0 149 In 2-d,
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36 SET-SHOW gnuplot 4.0 151 set xda
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36 SET-SHOW gnuplot 4.0 153 set zer
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38 SPLOT gnuplot 4.0 155 splot {}
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38 SPLOT gnuplot 4.0 157 Note that
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43 OLD BUGS gnuplot 4.0 159 be "old
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