# PyX — Example: axis/log.py

## Logarithmic axes

import fractions, math from pyx import * from pyx.graph import axis # we here use parters and texters which are explained in the examples below log2parter = axis.parter.log([axis.parter.preexp([axis.tick.rational(1)], 4), axis.parter.preexp([axis.tick.rational(1)], 2)]) log2texter = axis.texter.default(base=fractions.Fraction(2)) g = graph.graphxy(width=10, x=axis.log(min=1, max=1024), y=axis.log(min=1, max=1024, parter=log2parter), y2=axis.log(min=1, max=1024, parter=log2parter, texter=log2texter)) g.writeEPSfile("log") g.writePDFfile("log") g.writeSVGfile("log")

### Description

Logarithmic axes are quite similar to linear axes and differ only in a very few properties, namely a non-linear mapping of values to axis positions. They also have different default partitioners and raters (see below). While the partitioner really is quite different - it implements a logarithmic positioning of the ticks - the rater just alters some defaults in favour of using more subticks to improve the visualization of the logarithmic nature of the axis.

Besides presenting a standard logarithmic axis, we also show you how to alter the base used by the logarithmic axis. Since the functionality of a logarithmic axis is independent of the base, all we need to adjust are the components for creating ticks (see `log2parter`

) and the texts for the labels (see `log2texter`

). More details about the parters and texters components are given below in the corresponding examples.