Axes are a fundamental component of graphs although there might be applications outside of the graph system. Internally axes are constructed out of components, which handle different tasks axes need to fulfill:
Implements the conversion of a data value to a graph coordinate of range [0:1]. It does also handle the proper usage of the components in complicated tasks (i.e. combine the partitioner, texter, painter and rater to find the best partitioning).
An anchoredaxis is a container to combine an axis with an positioner and provide a storage area for all kind of axis data. That way axis instances are reusable (they do not store any data locally). The anchoredaxis and the positioner are created by a graph corresponding to its geometry.
The names above map directly to modules which are provided in the directory graph/axis except for the anchoredaxis, which is part of the axis module as well. Sometimes it might be convenient to import the axis directory directly rather than to access iit through the graph. This would look like:
from pyx import *
graph.axis.painter() # and the like
from pyx.graph import axis
axis.painter() # this is shorter ...
In most cases different implementations are available through different classes, which can be combined in various ways. There are various axis examples distributed with PyX, where you can see some of the features of the axis with a few lines of code each. Hence we can here directly come to the reference of the available components.
The following classes are part of the module graph.axis.axis. However, there is a shortcut to access those classes via graph.axis directly.
Instances of the following classes can be passed to the **axes keyword arguments of a graph. Those instances should only be used once.
This class provides a linear axis. min and max define the axis range. When not set, they are adjusted automatically by the data to be plotted in the graph. Note, that some data might want to access the range of an axis (e.g. the function class when no range was provided there) or you need to specify a range when using the axis without plugging it into a graph (e.g. when drawing an axis along a path). In cases where the data provides a range of zero (e.g. a when plotting a constant function), then a fallbackrange can be set to guarantee a minimal range of the axis.
reverse can be set to indicate a reversed axis starting with bigger values first. Alternatively you can fix the axis range by min and max accordingly. When divisor is set, it is taken to divide all data range and position informations while creating ticks. You can create ticks not taking into account a factor by that. title is the title of the axis.
parter is a partitioner instance, which creates suitable ticks for the axis range. Those ticks are merged with ticks manually given by manualticks before proceeding with rating, painting etc. Manually placed ticks win against those created by the partitioner. For automatic partitioners, which are able to calculate several possible tick lists for a given axis range, the density is a (linear) factor to favour more or less ticks. It should not be stressed to much (its likely, that the result would be unappropriate or not at all valid in terms of rating label distances). But within a range of say 0.5 to 2 (even bigger for large graphs) it can help to get less or more ticks than the default would lead to. maxworse is the number of trials with more and less ticks when a better rating was already found. rater is a rater instance, which rates the ticks and the label distances for being best suitable. It also takes into account density. The rater is only needed, when the partitioner creates several tick lists.
texter is a texter instance. It creates labels for those ticks, which claim to have a label, but do not have a label string set already. Ticks created by partitioners typically receive their label strings by texters. The painter is finally used to construct the output. Note, that usually several output constructions are needed, since the rater is also used to rate the distances between the labels for an optimum. The linkedpainter is used as the axis painter, when automatic link axes are created by the createlinked() method.
This class provides a logarithmic axis. All parameters work like linear. Only two parameters have a different default: parter and rater. Furthermore and most importantly, the mapping between data and graph coordinates is logarithmic.
This class is an abbreviation of logarithmic described above.
This class provides an axis suitable for a bar style. It handles a discrete set of values and maps them to distinct ranges in graph coordinates. For that, the axis gets a tuple of two values.
The first item is taken to be one of the discrete values valid on this axis. The discrete values can be any hashable type and the order of the subaxes is defined by the order the data is received or the inverse of that when reverse is set.
The second item is passed to the corresponding subaxis. The result of the conversion done by the subaxis is mapped to the graph coordinate range reserved for this subaxis. This range is defined by a size attribute of the subaxis, which can be added to any axis. (see the sized linear axes described below for some axes already having a size argument). When no size information is available for a subaxis, a size value of 1 is used. The baraxis itself calculates its size by suming up the sizes of its subaxes plus firstdist, lastdist and dist times the number of subaxes minus 1.
subaxes should be a list or a dictionary mapping a discrete value of the bar axis to the corresponding subaxis. When no subaxes are set or data is received for an unknown discrete axis value, instances of defaultsubaxis are used as the subaxis for this discrete value.
dist is used as the spacing between the ranges for each distinct value. It is measured in the same units as the subaxis results, thus the default value of 0.5 means half the width between the distinct values as the width for each distinct value. firstdist and lastdist are used before the first and after the last value. When set to None, half of dist is used.
title is the title of the split axes and painter is a specialized painter for an bar axis and linkpainter is used as the painter, when automatic link axes are created by the createlinked() method.
This class is identical to the bar axis except for the different default value for defaultsubaxis.
This class is identical to the bar axis except for the different default value for defaultsubaxis, firstdist, lastdist, painter, and linkedpainter.
Sometimes you want to alter the default size of 1 of the subaxes. For that you have to add a size attribute to the axis data. The two classes sizedlinear and autosizedlinear do that for linear axes. Their short names are sizedlin and autosizedlin. sizedlinear extends the usual linear axis by an first argument size. autosizedlinear creates the size out of its data range automatically but sets an autolinear parter with extendtick being None in order to disable automatic range modifications while painting the axis.
The axis module also contains classes implementing so called anchored axes, which combine an axis with an positioner and a storage place for axis related data. Since these features are not interesting for the average PyX user, we’ll not go into all the details of their parameters and except for some handy axis position methods:
Returns a path instance for the base path. x1 and x2 define the axis range, the base path should cover. For None the beginning and end of the path is taken, which might cover a longer range, when the axis is embedded as a subaxis. For that case, a None value extends the range to the point of the middle between two subaxes or the beginning or end of the whole axis, when the subaxis is the first or last of the subaxes.
Like basepath() but in graph coordinates.
Returns a path instance for the grid path at position x. Might return None when no grid path is available.
Like gridpath() but in graph coordinates.
Returns the position of x as a tuple (x, y).
Like tickpoint() but in graph coordinates.
Returns the direction of a tick at x as a tuple (dx, dy). The tick direction points inside of the graph.
Like tickdirection() but in graph coordinates.
Like tickdirection() but in graph coordinates.
However, there are two anchored axes implementations linkedaxis and anchoredpathaxis which are available to the user to create special forms of anchored axes.
This class implements an anchored axis to be passed to a graph constructor to manually link the axis to another anchored axis instance linkedaxis. Note that you can skip setting the value of linkedaxis in the constructor, but set it later on by the setlinkedaxis() method described below. errorname is printed within error messages when the data is used and some problem occurs. painter is used for painting the linked axis instead of the linkedpainter provided by the linkedaxis.
This method can be used to set the linkedaxis after constructing the axis. By that you can create several graph instances with cycled linked axes.
This class implements an anchored axis the path path. direction defines the direction of the ticks. Allowed values are 1 (left) and -1 (right).
The anchoredpathaxis contains as any anchored axis after calling its create() method the painted axis in the canvas member attribute. The function pathaxis() has the same signature like the anchoredpathaxis class, but immediately creates the axis and returns the painted axis.
The following classes are part of the module graph.axis.tick.
This class implements a rational number with infinite precision. For that it stores two integers, the numerator num and a denominator denom. Note that the implementation of rational number arithmetics is not at all complete and designed for its special use case of axis partitioning in PyX preventing any roundoff errors.
x is the value of the rational created by a conversion from one of the following input values:
floatprecision.
allowed to provide a fraction like "1/3".
denominator of the rational.
rational itself.
power is an integer to calculate x**power. This is useful at certain places in partitioners.
This class implements ticks based on rational numbers. Instances of this class can be passed to the manualticks parameter of a regular axis.
The parameters x, power, and floatprecision share its meaning with rational.
A tick has a tick level (i.e. markers at the axis path) and a label lavel (e.i. place text at the axis path), ticklevel and labellevel. These are non-negative integers or None. A value of 0 means a regular tick or label, 1 stands for a subtick or sublabel, 2 for subsubtick or subsublabel and so on. None means omitting the tick or label. label is the text of the label. When not set, it can be created automatically by a texter. labelattrs are the attributes for the labels.
The following classes are part of the module graph.axis.parter. Instances of the classes can be passed to the parter keyword argument of regular axes.
Instances of this class creates equally spaced tick lists. The distances between the ticks, subticks, subsubticks etc. starting from a tick at zero are given as first, second, third etc. item of the list tickdists. For a tick position, the lowest level wins, i.e. for [2, 1] even numbers will have ticks whereas subticks are placed at odd integer. The items of tickdists might be strings, floats or tuples as described for the pos parameter of class tick.
labeldists works equally for placing labels. When labeldists is kept None, labels will be placed at each tick position, but sublabels etc. will not be used. This copy behaviour is also available vice versa and can be disabled by an empty list.
extendtick can be set to a tick level for including the next tick of that level when the data exceeds the range covered by the ticks by more than epsilon. epsilon is taken relative to the axis range. extendtick is disabled when set to None or for fixed range axes. extendlabel works similar to extendtick but for labels.
Instances of this class creates equally spaced tick lists, where the distance between the ticks is adjusted to the range of the axis automatically. Variants are a list of possible choices for tickdists of linear. Further variants are build out of these by multiplying or dividing all the values by multiples of 10. variants should be ordered that way, that the number of ticks for a given range will decrease, hence the distances between the ticks should increase within the variants list. extendtick and epsilon have the same meaning as in linear.
[[tick.rational((1, 1)), tick.rational((1, 2))], [tick.rational((2, 1)), tick.rational((1, 1))], [tick.rational((5, 2)), tick.rational((5, 4))], [tick.rational((5, 1)), tick.rational((5, 2))]]
This class is an abbreviation of autolinear described above.
This is a storage class defining positions of ticks on a logarithmic scale. It contains a list pres of positions \(p_i\) and exp, a multiplicator \(m\). Valid tick positions are defined by \(p_im^n\) for any integer \(n\).
Instances of this class creates tick lists suitable to logarithmic axes. The positions of the ticks, subticks, subsubticks etc. are defined by the first, second, third etc. item of the list tickpreexps, which are all preexp instances.
labelpreexps works equally for placing labels. When labelpreexps is kept None, labels will be placed at each tick position, but sublabels etc. will not be used. This copy behaviour is also available vice versa and can be disabled by an empty list.
extendtick, extendlabel and epsilon have the same meaning as in linear.
Some preexp instances for the use in logarithmic are available as instance variables (should be used read-only):
preexp([tick.rational((1, 1))], 100000)
preexp([tick.rational((1, 1))], 10000)
preexp([tick.rational((1, 1))], 1000)
preexp([tick.rational((1, 1))], 100)
preexp([tick.rational((1, 1))], 10)
preexp([tick.rational((1, 1)), tick.rational((2, 1)), tick.rational((5, 1))], 10)
preexp([tick.rational((1, 1)) for x in range(1, 10)], 10)
This class is an abbreviation of logarithmic described above.
Instances of this class creates tick lists suitable to logarithmic axes, where the distance between the ticks is adjusted to the range of the axis automatically. Variants are a list of tuples with possible choices for tickpreexps and labelpreexps of logarithmic. variants should be ordered that way, that the number of ticks for a given range will decrease within the variants list.
extendtick, extendlabel and epsilon have the same meaning as in linear.
[([log.pre1exp, log.pre1to9exp], [log.pre1exp, log.pre125exp]), ([log.pre1exp, log.pre1to9exp], None), ([log.pre1exp2, log.pre1exp], None), ([log.pre1exp3, log.pre1exp], None), ([log.pre1exp4, log.pre1exp], None), ([log.pre1exp5, log.pre1exp], None)]
This class is an abbreviation of autologarithmic described above.
The following classes are part of the module graph.axis.texter. Instances of the classes can be passed to the texter keyword argument of regular axes. Texters are used to define the label text for ticks, which request to have a label, but for which no label text has been specified so far. A typical case are ticks created by partitioners described above.
Instances of this class create decimal formatted labels.
The strings prefix, infix, and suffix are added to the label at the beginning, immediately after the plus or minus, and at the end, respectively. decimalsep, thousandsep, and thousandthpartsep are strings used to separate integer from fractional part and three-digit groups in the integer and fractional part. The strings plus and minus are inserted in front of the unsigned value for non-negative and negative numbers, respectively.
The format string period should generate a period. It must contain one string insert operators %s for the period.
labelattrs is a list of attributes to be added to the label attributes given in the painter. It should be used to setup TeX features like text.mathmode. Text format options like text.size should instead be set at the painter.
Instances of this class create decimal formatted labels with an exponential.
The strings plus and minus are inserted in front of the unsigned value of the exponent.
The format string mantissaexp should generate the exponent. It must contain two string insert operators %s, the first for the mantissa and the second for the exponent. An alternative to the default is r"{{%s}{\rm e}{%s}}".
The format string skipexp0 is used to skip exponent 0 and must contain one string insert operator %s for the mantissa. None turns off the special handling of exponent 0. The format string skipexp1 is similar to skipexp0, but for exponent 1.
The format string nomantissaexp is used to skip the mantissa 1 and must contain one string insert operator %s for the exponent. None turns off the special handling of mantissa 1. The format string minusnomantissaexp is similar to nomantissaexp, but for mantissa -1.
The tick.rational instances mantissamin*< *mantissamax are minimum (including) and maximum (excluding) of the mantissa.
The boolean skipmantissa1 enables the skipping of any mantissa equals 1 and -1, when minusnomantissaexp is set. When the boolean skipallmantissa1 is set, a mantissa equals 1 is skipped only, when all mantissa values are 1. Skipping of a mantissa is stronger than the skipping of an exponent.
mantissatexter is a texter instance for the mantissa.
Instances of this class create decimal formatted labels with an exponential, when the unsigned values are small or large compared to 1.
The rational instances smallestdecimal and biggestdecimal are the smallest and biggest decimal values, where the decimal texter should be used. The sign of the value is ignored here. For a tick at zero the decimal texter is considered best as well. equaldecision is a boolean to indicate whether the decision for the decimal or exponential texter should be done globally for all ticks.
decimal and exponential are a decimal and an exponential texter instance, respectively.
Instances of this class create labels formated as fractions.
The strings prefix, infix, and suffix are added to the label at the beginning, immediately after the plus or minus, and at the end, respectively. The strings numprefix, numinfix, and numsuffix are added to the labels numerator accordingly whereas denomprefix, denominfix, and denomsuffix do the same for the denominator.
The strings plus and minus are inserted in front of the unsigned value. The position of the sign is defined by minuspos with values 1 (at the numerator), 0 (in front of the fraction), and -1 (at the denominator).
The format string over should generate the fraction. It must contain two string insert operators %s, the first for the numerator and the second for the denominator. An alternative to the default is "{{%s}/{%s}}".
Usually, the numerator and denominator are canceled, while, when equaldenom is set, the least common multiple of all denominators is used.
The boolean skip1 indicates, that only the prefix, plus or minus, the infix and the suffix should be printed, when the value is 1 or -1 and at least one of prefix, infix and suffix is present.
The boolean skipnum0 indicates, that only a 0 is printed when the numerator is zero.
skipnum1 is like skip1 but for the numerator.
skipdenom1 skips the denominator, when it is 1 taking into account denomprefix, denominfix, denomsuffix minuspos and the sign of the number.
labelattrs has the same meaning as for decimal.
The following classes are part of the module graph.axis.painter. Instances of the painter classes can be passed to the painter keyword argument of regular axes.
This helper class is used in direction arguments of the painters below to prevent axis labels and titles being written upside down. In those cases the text will be rotated by 180 degrees. direction is an angle to be used relative to the tick direction. epsilon is the value by which 90 degrees can be exceeded before an 180 degree rotation is performed.
The following two class variables are initialized for the most common applications:
rotatetext(90)
rotatetext(180)
This helper class provides changeable PyX lengths starting from an initial value initial multiplied by factor again and again. The resulting lengths are thus a geometric series.
There are some class variables initialized with suitable values for tick stroking. They are named ticklength.SHORT, ticklength.SHORt, …, ticklength.short, ticklength.normal, ticklength.long, …, ticklength.LONG. ticklength.normal is initialized with a length of 0.12 and the reciprocal of the golden mean as factor whereas the others have a modified initial value obtained by multiplication with or division by appropriate multiples of \(\sqrt{2}\).
Instances of this class are painters for regular axes like linear and logarithmic axes.
innerticklength and outerticklength are visual PyX lengths of the ticks, subticks, subsubticks etc. plotted along the axis inside and outside of the graph. Provide changeable attributes to modify the lengths of ticks compared to subticks etc. None turns off the ticks inside and outside the graph, respectively.
tickattrs and gridattrs are changeable stroke attributes for the ticks and the grid, where None turns off the feature. basepathattrs are stroke attributes for the axis or None to turn it off. basepathattrs is merged with [style.linecap.square].
labeldist is the distance of the labels from the axis base path as a visual PyX length. labelattrs is a list of text attributes for the labels. It is merged with [text.halign.center, text.vshift.mathaxis]. labeldirection is an instance of rotatetext to rotate the labels relative to the axis tick direction or None.
The boolean values labelhequalize and labelvequalize force an equal alignment of all labels for straight vertical and horizontal axes, respectively.
titledist is the distance of the title from the rest of the axis as a visual PyX length. titleattrs is a list of text attributes for the title. It is merged with [text.halign.center, text.vshift.mathaxis]. titledirection is an instance of rotatetext to rotate the title relative to the axis tick direction or None. titlepos is the position of the title in graph coordinates.
texrunner is the texrunner instance to create axis text like the axis title or labels. When not set the texrunner of the graph instance is taken to create the text.
This class is identical to regular up to the default values of labelattrs and titleattrs. By turning off those features, this painter is suitable for linked axes.
Instances of this class are suitable painters for bar axes.
innerticklength and outerticklength are visual PyX lengths to mark the different bar regions along the axis inside and outside of the graph. None turns off the ticks inside and outside the graph, respectively. tickattrs are stroke attributes for the ticks or None to turn all ticks off.
The parameters with prefix name are identical to their label counterparts in regular. All other parameters have the same meaning as in regular.
This class is identical to bar up to the default values of nameattrs and titleattrs. By turning off those features, this painter is suitable for linked bar axes.
Instances of this class are suitable painters for split axes.
breaklinesdist and breaklineslength are the distance between axes break markers in visual PyX lengths. breaklinesangle is the angle of the axis break marker with respect to the base path of the axis. All other parameters have the same meaning as in regular.
This class is identical to split up to the default value of titleattrs. By turning off this feature, this painter is suitable for linked split axes.
The rating of axes is implemented in graph.axis.rater. When an axis partitioning scheme returns several partitioning possibilities, the partitions need to be rated by a positive number. The axis partitioning rated lowest is considered best.
The rating consists of two steps. The first takes into account only the number of ticks, subticks, labels and so on in comparison to optimal numbers. Additionally, the extension of the axis range by ticks and labels is taken into account. This rating leads to a preselection of possible partitions. In the second step, after the layout of preferred partitionings has been calculated, the distance of the labels in a partition is taken into account as well at a smaller weight factor by default. Thereby partitions with overlapping labels will be rejected completely. Exceptionally sparse or dense labels will receive a bad rating as well.
Instances of this class provide a number rater. opt is the optimal value. When not provided, left is set to 0 and right is set to 3*opt. Weight is a multiplicator to the result.
The rater calculates width*((x-opt)/(other-opt))**3 to rate the value x, where other is left (x``<*opt*) or *right* (``x>*opt*).
Instances of this class provide a rater for a list of numbers. The purpose is to rate the distance between label boxes. opt is the optimal value.
The rater calculates the sum of weight*(opt/x-1) (x``<*opt*) or ``weight*(x/opt-1) (x>*opt*) for all elements x of the list. It returns this value divided by the number of elements in the list.
Instances of this class are raters for axes partitionings.
ticks and labels are both lists of number rater instances, where the first items are used for the number of ticks and labels, the second items are used for the number of subticks (including the ticks) and sublabels (including the labels) and so on until the end of the list is reached or no corresponding ticks are available.
range is a number rater instance which rates the range of the ticks relative to the range of the data.
distance is an distance rater instance.
This class is suitable to rate partitionings of linear axes. It is equal to rater but defines predefined values for the arguments.
This class is suitable to rate partitionings of logarithmic axes. It is equal to rater but defines predefined values for the arguments.
This class is an abbreviation of logarithmic described above.
The position of an axis is defined by an instance of a class providing the following methods:
Returns a path instance for the base path. v1 and v2 define the axis range in graph coordinates the base path should cover.
Returns a path instance for the grid path at position v in graph coordinates. The method might return None when no grid path is available (for an axis along a path for example).
Returns the position of v in graph coordinates as a tuple (x, y) in points.
Returns the direction of a tick at v in graph coordinates as a tuple (dx, dy). The tick direction points inside of the graph.
The module contains several implementations of those positioners, but since the positioner instances are created by graphs etc. as needed, the details are not interesting for the average PyX user.