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4.4.3.4 Cartesian exponential axes

Normally, stride will be used to create equidistant (in the user's unit) annotations or ticks, but because of the exponential nature of the axis, such annotations may converge on each other at one end of the axis. To avoid this problem, you can append p to stride, and the annotation interval is expected to be in transformed units, yet the annotation itself will be plotted as un-transformed units. E.g., if stride = 1 and power = 0.5 (i.e., sqrt), then equidistant annotations labeled 1, 4, 9, ... will appear.

Figure 4.10: Exponential or power projection axis. (top) Using an exponent of 0.5 yields a $\sqrt {x}$ axis. Here, intervals refer to actual data values, in -R0/100/0/1 -JX3p0.5/0.4 -Ba20f10g5. (bottom) Here, intervals refer to projected values, although the annotation uses the corresponding unprojected values, as in -Ba3f2g1p.
\begin{figure}\centering\epsfig{figure=eps/GMT_-B_pow.eps}\end{figure}


next up previous contents index
Next: 4.4.3.5 Cartesian time axes Up: 4.4.3 Map frame and Previous: 4.4.3.3 Cartesian log axes   Contents   Index
Paul Wessel 2004-10-01