gnuplot documentation

48 gnuplot 4.3 35 LABELS
plane along two, not necessarily orthogonal, directions. In other words, groups of four adjacent points
are assumed to form the same size parallelogram. The variable value in the tuples represent a palette
color (gray value) for indexing in the current palette.
Each pixel (data point) of the input 2D image will become a rectangle or parallelipiped in theplot. The
coordinate of each data point will determine the center of the parallelipiped. That is, an M x N set of
data will form an image with M x N pixels. This is slightly different than pm3d elements where an M x
N set of data will form a surface of (M-1) x (N-1) elements. The scan directions for the image data grid
can be any of eight possible combinations.
See also rgbimage (p. 50).
33.1 Image failsafe
Some terminal drivers provide code to optimize rendering of image data within a rectangular 2D area.
However this code is known to be imperfect (hence the label EXPERIMENTAL for image support in
gnuplot version 4.2). This optimized code may be disabled by using the keyword failsafe. E.g.
plot ’data’ with image failsafe
Here are some specific comments about particular terminal drivers:
x11 and wxt - Pixels are either repeated or decimated to fit the display resolution; no other processing
(filtering) is done. Thus, aliasing may occur when decimating images having high spatial frequency
content.
postscript (pslatex, epslatex, pstex) - Image is copied in its original resolution, and sample interpolation
is turned off.
See also rgbimage (p. 50).
34 Impulses
The impulses style displays a vertical line from the
x axis (2D) or from the xy plane (3D) to each input
point. To use this style effectively in 3D plots, it is
useful to use thick lines (linewidth > 1).
1 column: y # implicit x coordinate from row number (2D)
2 columns: x y # line from [x,0] to [x,y] (2D)
3 columns: x y z # line from [x,y,0] to [x,y,z] (3D)
with impulses
35 Labels
The labels style reads coordinates and text from
a data file and places the text string at the corresponding
2D or 3D position. 3 or 4 input columns of
basic data are required. Additional input columns
may be used to provide information such as variable
text color (see rgbcolor variable (p. 33)).
3 columns: x y string # 2D version
4 columns: x y z string # 3D version
EF
FG GHI
HIJ
IJK
JKLM
KLM
with labels
LMNO
MNOP
N
O PQRS
The font, color, rotation angle and other properties of the printed text may be specified as additional
command options (see set label (p. 109)). The example below will generate a 2D plot with text labels
taken from column 4 of the input file (tc lt 2 is shorthand for textcolor linetype 2, which is green).
plot ’datafile’ using 1:(0.5 * $2):4 with labels font "arial,11" tc lt 2
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