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<H1><A NAME="SECTION000600000000000000000"></A><a id='l2h-24' xml:id='l2h-24'></a>
<BR>
6 Area
</H1>
<A NAME="module-area"></A>
<P>
<dl><dt><b><span class="typelabel">class</span> <tt id='l2h-26' xml:id='l2h-26' class="class">area.T</tt></b>
<dd>
Class <code>area.T</code> defines the location and size of a chart. It also
defines the coordinate system (linear, log, or enumeration) of the X and
Y axes.
<P>
<a id='l2h-27' xml:id='l2h-27'></a><a id='l2h-28' xml:id='l2h-28'></a>
The X (or Y) coordinate system is defined by attribute
<code>x_coord</code> (or <code>y_coord</code>), which takes an object
of type <code>coord.T</code>. Class <code>coord.T</code> defines how an X (or a Y)
value is mapped to a display (canvas) location. PyChart provides
three standard coordinate systems: <code>linear_coord.T</code> (for linear
mapping; this is the default), <code>log_coord.T</code> (for logarithmic
mapping), and <code>category_coord.T</code> (enumeration of values). Most
charts will do ok by instantiating one of these pre-defined coordinate
classes, but you can also define your own wacky coordinate system.
<P>
<div class="seealso">
<p class="heading">See Also:</p>
See Section <A href="module-coord.html#module-coord">6.1</A> for more about the coordinate system.
</div>
<P>
For log and linear coordinate systems, the minimum and maximum
displayable values in the area are computed automatically from the plots
unless they are defined explicitly via attribute <code>x_range</code>.
In the next example, the X axis is drawn with a
logarithmic scale. The minimum value
will be 10, and the maximum value will be computed from the values given
to plots.
<P>
<div class="verbatim"><pre>
ar = <a href="module-area.html">area.T</a>(x_coord = <a href="module-coord.html">log_coord.T</a>(), x_range = (10, None), ...)
</pre></div>
<P>
In the below example of a category coordinate system,
the X axis will list three strings,
``apple'', ``orange'', and ``blueberry''.
<P>
<div class="verbatim"><pre>
samples = [("apple", 10), ("orange", 30), ("blueberry", 20)],
ar = <a href="module-area.html">area.T</a>(x_coord = category_coord(samples, 0))
ar.add_plot(<a href="module-bar-plot.html">bar_plot.T</a>(data = samples))
</pre></div>
</dl>
<P>
We now list the attributes understood by an <code>area.T</code> object.
<P>
<dl><dt><b><tt id='l2h-29' xml:id='l2h-29' class="member">bg_style</tt></b></dt>
<dd>
<b>Type:</b> fill_style.T
( see Section <A href="module-fill-style.html#module-fill-style">16</A>)
<b>Default:</b> None.
<P>
Background fill-pattern.
</dl>
<dl><dt><b><tt id='l2h-30' xml:id='l2h-30' class="member">border_line_style</tt></b></dt>
<dd>
<b>Type:</b> line_style.T
( see Section <A href="module-line-style.html#module-line-style">14</A>)
<b>Default:</b> None.
<P>
Line style of the outer frame of the chart.
</dl>
<dl><dt><b><tt id='l2h-31' xml:id='l2h-31' class="member">legend</tt></b></dt>
<dd>
<b>Type:</b> legend.T
( see Section <A href="module-legend.html#module-legend">6.3</A>)
<b>Default:</b> a legend is by default displayed
in the right-center of the chart. If you don't want to draw
a legend, you should explicitly set None to this attribute..
<P>
The legend of the chart.
</dl>
<dl><dt><b><tt id='l2h-32' xml:id='l2h-32' class="member">loc</tt></b></dt>
<dd>
<b>Type:</b> (x,y) or None
<b>Default:</b> (0, 0).
<P>
The location of the bottom-left corner of the chart.
None means to use the default value.
<P>
</dl>
<dl><dt><b><tt id='l2h-33' xml:id='l2h-33' class="member">size</tt></b></dt>
<dd>
<b>Type:</b> (x,y) or None
<b>Default:</b> (120, 110).
<P>
The size of the chart-drawing area, excluding axis labels,
legends, tick marks, etc. None means to use the default value.
<P>
</dl>
<dl><dt><b><tt id='l2h-34' xml:id='l2h-34' class="member">x_axis</tt></b></dt>
<dd>
<b>Type:</b> axis.X
<b>Default:</b> None.
<P>
The X axis. See Section <A href="module-axis.html#module-axis">6.2</A>.
</dl>
<dl><dt><b><tt id='l2h-35' xml:id='l2h-35' class="member">x_axis2</tt></b></dt>
<dd>
<b>Type:</b> axis.X
<b>Default:</b> None.
<P>
The second X axis. This axis should be non-None either when you want to display plots with two distinct domains or when
you just want to display two axes at the top and bottom of the chart.
See Section <A href="module-axis.html#module-axis">6.2</A>
</dl>
<dl><dt><b><tt id='l2h-36' xml:id='l2h-36' class="member">x_coord</tt></b></dt>
<dd>
<b>Type:</b> coord.T
(see Section <A href="module-coord.html#module-coord">6.1</A>)
<b>Default:</b> A linear coordinate system..
<P>
Set the X coordinate system.
</dl>
<dl><dt><b><tt id='l2h-37' xml:id='l2h-37' class="member">x_grid_interval</tt></b></dt>
<dd>
<b>Type:</b> number or function
<b>Default:</b> None.
<P>
The horizontal grid-line interval.
A numeric value
specifies the interval at which
lines are drawn. If value is a function, it
takes two arguments, (MIN, MAX), that tells
the minimum and maximum values found in the
sample data. The function should return a list
of values at which lines are drawn.
</dl>
<dl><dt><b><tt id='l2h-38' xml:id='l2h-38' class="member">x_grid_over_plot</tt></b></dt>
<dd>
<b>Type:</b> bool
<b>Default:</b> False.
<P>
If True, grid lines are drawn over plots. Otherwise, plots are drawn over grid lines.
</dl>
<dl><dt><b><tt id='l2h-39' xml:id='l2h-39' class="member">x_grid_style</tt></b></dt>
<dd>
<b>Type:</b> line_style.T
( see Section <A href="module-line-style.html#module-line-style">14</A>)
<b>Default:</b> None.
<P>
The style of horizontal grid lines.
</dl>
<dl><dt><b><tt id='l2h-40' xml:id='l2h-40' class="member">x_range</tt></b></dt>
<dd>
<b>Type:</b> (x,y) or None
<b>Default:</b> None.
<P>
Specifies the range of X values that are displayed in the
chart. IF the value is None, both the values are computed
automatically from the samples. Otherwise, the value must be a
tuple of format (MIN, MAX). MIN and MAX must be either None or a
number. If None, the value is computed automatically from the
samples. For example, if x_range = (None,5), then the minimum X
value is computed automatically, but the maximum X value is fixed
at 5.
</dl>
<dl><dt><b><tt id='l2h-41' xml:id='l2h-41' class="member">y_axis</tt></b></dt>
<dd>
<b>Type:</b> axis.Y
<b>Default:</b> None.
<P>
The Y axis. See Section <A href="module-axis.html#module-axis">6.2</A>.
</dl>
<dl><dt><b><tt id='l2h-42' xml:id='l2h-42' class="member">y_axis2</tt></b></dt>
<dd>
<b>Type:</b> axis.Y
<b>Default:</b> None.
<P>
The second Y axis. This axis should be non-None either when you want to display plots with two distinct ranges or when
you just want to display two axes at the left and right of the chart. See Section <A href="module-axis.html#module-axis">6.2</A>
</dl>
<dl><dt><b><tt id='l2h-43' xml:id='l2h-43' class="member">y_coord</tt></b></dt>
<dd>
<b>Type:</b> coord.T
(see Section <A href="module-coord.html#module-coord">6.1</A>)
<b>Default:</b> A linear coordinate system..
<P>
Set the Y coordinate system.
</dl>
<dl><dt><b><tt id='l2h-44' xml:id='l2h-44' class="member">y_grid_interval</tt></b></dt>
<dd>
<b>Type:</b> number or function
<b>Default:</b> None.
<P>
The vertical grid-line interval. See also x_grid_interval
</dl>
<dl><dt><b><tt id='l2h-45' xml:id='l2h-45' class="member">y_grid_over_plot</tt></b></dt>
<dd>
<b>Type:</b> int
<b>Default:</b> False.
<P>
See x_grid_over_plot.
</dl>
<dl><dt><b><tt id='l2h-46' xml:id='l2h-46' class="member">y_grid_style</tt></b></dt>
<dd>
<b>Type:</b> line_style.T
( see Section <A href="module-line-style.html#module-line-style">14</A>)
<b>Default:</b> line_style.gray70_dash3.
<P>
The style of vertical grid lines.
</dl>
<dl><dt><b><tt id='l2h-47' xml:id='l2h-47' class="member">y_range</tt></b></dt>
<dd>
<b>Type:</b> (x,y) or None
<b>Default:</b> None.
<P>
Specifies the range of Y values that are displayed in the
chart. IF the value is None, both the values are computed
automatically from the samples. Otherwise, the value must be a
tuple of format (MIN, MAX). MIN and MAX must be either None or a
number. If None, the value is computed automatically from the
samples. For example, if y_range = (None,5), then the minimum Y
value is computed automatically, but the maximum Y value is fixed
at 5.
</dl>
<P>
An object of <code>area.T</code> also provides several methods:
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-48' xml:id='l2h-48' class="method">add_plot</tt></b>(</nobr></td>
<td><var>plot, ...</var>)</td></tr></table></dt>
<dd>
Add plots to the area. Each <var>plot</var> must be a plot object.
See Section <A href="module-line-plot.html#module-line-plot">9</A>, Section <A href="module-bar-plot.html#module-bar-plot">7</A>,
Section <A href="module-pie-plot.html#module-pie-plot">11</A>, Section <A href="module-range-plot.html#module-range-plot">10</A>.
</dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-49' xml:id='l2h-49' class="method">draw</tt></b>(</nobr></td>
<td><var>canvas = None</var>)</td></tr></table></dt>
<dd>
Draw plots, axes, and the legend. This procedure must be called at the
end of every PyChart application.
Parameter <var>canvas</var> is an optional parameter that specifies the output.
If omitted, the default canvas is used.
<div class="seealso">
<p class="heading">See Also:</p>
Section <A href="module-canvas.html#module-canvas">21</A> for more about canvas.
</div>
</dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-50' xml:id='l2h-50' class="method">x_pos</tt></b>(</nobr></td>
<td><var>xval</var>)</td></tr></table></dt>
<dd>
Converts <var>xval</var> to a coordinate on the canvas ( see Section <A href="module-canvas.html#module-canvas">21</A>).
See Section <A href="unit.html#unit">4</A>.
</dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
<td><nobr><b><tt id='l2h-51' xml:id='l2h-51' class="method">y_pos</tt></b>(</nobr></td>
<td><var>yval</var>)</td></tr></table></dt>
<dd>
Converts <var>yval</var> to a coordinate on the canvas ( see Section <A href="module-canvas.html#module-canvas">21</A>).
See Section <A href="unit.html#unit">4</A>.
</dl>
<P>
<div class="verbatim"><pre>
ar = <a href="module-area.html">area.T</a>(loc=(50, 50), size=(100, 100),
xrange=(0,200), yrange=(0, 1000))
px = ar.x_pos(50)
py = ar.y_pos(100)
</pre></div>
<P>
In the above example, the chart is drawn in the area defined by
rectangle (50, 50) - (150, 150). The point (<code>px, py</code>) will
be at (75, 60), which is the screen location at which the point
(50, 100) would be drawn (i.e., 50 + 100 * 50/200 = 75,
50 + 100 * 100 / 1000 = 60).
<P>
<P>
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