QPlot: gline

gline Generalized line drawing

Call signature:

gline(ptspecs)

Help text:

gline([ptspec1, ptspec2, ...]).
a ptspec is a list containing commands from the following list:

AbsData(x, y) - Absolute data coordinates
RelData(dx, dy) - Relative data coordinates
AbsPaper(x, y) - Absolute paper coordinates (in pt)
RelPaper(dx, dy) - Relative data coordinates (in pt)
RotData(xi, eta) - Rotate by atan2(eta, xi) in data space.
                    (This affects subsequent relative positioning.)
RotPaper(phi) - Rotate by phi radians. (This affects subsequent
                    relative positioning.)
Retract(l) - Retract preceding and following segments by l pt.
Retract(l1, l2) - Retract preceding and following segments by l1 and
                    l2 pt respectively.
At(id) - Absolute paper coordinates of location set by at.
AtX(id) - Absolute paper x-coordinate of location set by at.
AtY(id) - Absolute paper y-coordinate of location set by at.

For instance,

gline([[AbsData(0, 1), RelPaper(5,0)],
[AbsData(2, 3), RelPaper(0, 7)]])

draws a line from 5 pt to the right of the point (0, 1) in the graph to 7 pt below the point (2, 3) in the graph. (Note that paper y-coordinates increase toward the bottom of the graph while data y-coordinates increase toward the top.) Note: The rather cumbersome syntax of gline makes line and plot more attractive for general usage. The same applies to garea versus area and patch. See also shiftedline and gline2.

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Example:

import pyqplot as qp

import numpy as np

qp.figure('gline', 3, 3)

xx = np.arange(-1.5*np.pi, 1.5*np.pi)

yy = np.cos(xx)

qp.marker('o', fill='solid')

qp.mark(xx, yy)

N=len(xx)

for n in range(N-1):

qp.gline([[qp.AbsData(xx[n], yy[n]), qp.Retract(10)],

[qp.AbsData(xx[n+1],yy[n+1]), qp.Retract(10)]])

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