gbrault
/
jupytersketcher
镜像来自 https://github.com/gbrault/jupytersketcher.git


			
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     <!-- navigation toc: --> <li><a href="._pysketcher002.html#___sec0" style="font-size: 80%;"><b>A first glimpse of Pysketcher</b></a></li>
     <!-- navigation toc: --> <li><a href="._pysketcher002.html#___sec1" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Basic construction of sketches</a></li>
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     <!-- navigation toc: --> <li><a href="._pysketcher003.html#sketcher:ex:pendulum" style="font-size: 80%;"><b>A simple pendulum</b></a></li>
     <!-- navigation toc: --> <li><a href="._pysketcher003.html#sketcher:ex:pendulum:basic" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;The basic physics sketch</a></li>
     <!-- navigation toc: --> <li><a href="._pysketcher003.html#___sec10" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;The body diagram</a></li>
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     <!-- navigation toc: --> <li><a href="#___sec16" style="font-size: 80%;"><b>Basic shapes</b></a></li>
     <!-- navigation toc: --> <li><a href="#___sec17" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Axis</a></li>
     <!-- navigation toc: --> <li><a href="#___sec18" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Distance with text</a></li>
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     <!-- navigation toc: --> <li><a href="#___sec23" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Dashpot</a></li>
     <!-- navigation toc: --> <li><a href="#___sec24" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Wavy</a></li>
     <!-- navigation toc: --> <li><a href="#___sec25" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Stochastic curves</a></li>
     <!-- navigation toc: --> <li><a href="._pysketcher005.html#___sec26" style="font-size: 80%;"><b>Inner workings of the Pysketcher tool</b></a></li>
     <!-- navigation toc: --> <li><a href="._pysketcher005.html#___sec27" style="font-size: 80%;">&nbsp;&nbsp;&nbsp;Example of classes for geometric objects</a></li>
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<h1 id="___sec16">Basic shapes </h1>

<p>
This section presents many of the basic shapes in Pysketcher:
<code>Axis</code>, <code>Distance_wText</code>, <code>Rectangle</code>, 	<code>Triangle</code>, <code>Arc</code>,
<code>Spring</code>, <code>Dashpot</code>, and <code>Wavy</code>.
Each shape is demonstrated with a figure and a
unit test that shows how the figure is constructed in Python code.
These demos rely heavily on the method <code>draw_dimensions</code> in
the shape classes, which annotates the basic drawing of the shape
with the various geometric parameters that govern the shape.

<h2 id="___sec17">Axis </h2>

<p>
The <code>Axis</code> object gives the possibility draw a single axis to
notify a coordinate system. Here is an example where we
draw \( x \) and \( y \) axis of three coordinate systems of different
rotation:

<p>
<br />
<br />

<p>
<center><p><img src="fig-tut/Axis.png" align="bottom" width=500></p></center>

<p>
<br />
<br />

<p>
The corresponding code looks like this:

<p>

<!-- code=python (!bc pycod) typeset with pygments style "default" -->
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%"><span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">test_Axis</span>():
    drawing_tool<span style="color: #666666">.</span>set_coordinate_system(
        xmin<span style="color: #666666">=0</span>, xmax<span style="color: #666666">=15</span>, ymin<span style="color: #666666">=-7</span>, ymax<span style="color: #666666">=8</span>, axis<span style="color: #666666">=</span><span style="color: #008000">True</span>,
        instruction_file<span style="color: #666666">=</span><span style="color: #BA2121">&#39;tmp_Axis.py&#39;</span>)
    <span style="color: #408080; font-style: italic"># Draw normal x and y axis with origin at (7.5, 2)</span>
    <span style="color: #408080; font-style: italic"># in the coordinate system of the sketch: [0,15]x[-7,8]</span>
    x_axis <span style="color: #666666">=</span> Axis((<span style="color: #666666">7.5</span>,<span style="color: #666666">2</span>), <span style="color: #666666">5</span>, <span style="color: #BA2121">&#39;x&#39;</span>, rotation_angle<span style="color: #666666">=0</span>)
    y_axis <span style="color: #666666">=</span> Axis((<span style="color: #666666">7.5</span>,<span style="color: #666666">2</span>), <span style="color: #666666">5</span>, <span style="color: #BA2121">&#39;y&#39;</span>, rotation_angle<span style="color: #666666">=90</span>)
    system <span style="color: #666666">=</span> Composition({<span style="color: #BA2121">&#39;x axis&#39;</span>: x_axis, <span style="color: #BA2121">&#39;y axis&#39;</span>: y_axis})
    system<span style="color: #666666">.</span>draw()
    drawing_tool<span style="color: #666666">.</span>display()

    <span style="color: #408080; font-style: italic"># Rotate this system 40 degrees counter clockwise</span>
    <span style="color: #408080; font-style: italic"># and draw it with dashed lines</span>
    system<span style="color: #666666">.</span>set_linestyle(<span style="color: #BA2121">&#39;dashed&#39;</span>)
    system<span style="color: #666666">.</span>rotate(<span style="color: #666666">40</span>, (<span style="color: #666666">7.5</span>,<span style="color: #666666">2</span>))
    system<span style="color: #666666">.</span>draw()
    drawing_tool<span style="color: #666666">.</span>display()

    <span style="color: #408080; font-style: italic"># Rotate this system another 220 degrees and show</span>
    <span style="color: #408080; font-style: italic"># with dotted lines</span>
    system<span style="color: #666666">.</span>set_linestyle(<span style="color: #BA2121">&#39;dotted&#39;</span>)
    system<span style="color: #666666">.</span>rotate(<span style="color: #666666">220</span>, (<span style="color: #666666">7.5</span>,<span style="color: #666666">2</span>))
    system<span style="color: #666666">.</span>draw()
    drawing_tool<span style="color: #666666">.</span>display()

    drawing_tool<span style="color: #666666">.</span>display(<span style="color: #BA2121">&#39;Axis&#39;</span>)
</pre></div>

<h2 id="___sec18">Distance with text </h2>

<p>
The object <code>Distance_wText</code> is used to display an arrow, to indicate
a distance in a sketch, with an additional text in the middle of the arrow.

<p>
The figure

<p>
<br />
<br />

<p>
<center><p><img src="fig-tut/Distance_wText.png" align="bottom" width=500></p></center>

<p>
<br />
<br />

<p>
was produced by this code:

<p>

<!-- code=python (!bc pycod) typeset with pygments style "default" -->
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%"><span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">test_Distance_wText</span>():
    drawing_tool<span style="color: #666666">.</span>set_coordinate_system(
        xmin<span style="color: #666666">=0</span>, xmax<span style="color: #666666">=10</span>, ymin<span style="color: #666666">=0</span>, ymax<span style="color: #666666">=6</span>,
        axis<span style="color: #666666">=</span><span style="color: #008000">True</span>, instruction_file<span style="color: #666666">=</span><span style="color: #BA2121">&#39;tmp_Distance_wText.py&#39;</span>)

    fontsize<span style="color: #666666">=14</span>
    t <span style="color: #666666">=</span> <span style="color: #BA2121">r&#39;$ 2\pi R^2 $&#39;</span>  <span style="color: #408080; font-style: italic"># sample text</span>
    examples <span style="color: #666666">=</span> Composition({
        <span style="color: #BA2121">&#39;a0&#39;</span>: Distance_wText((<span style="color: #666666">4</span>,<span style="color: #666666">5</span>), (<span style="color: #666666">8</span>, <span style="color: #666666">5</span>), t, fontsize),
        <span style="color: #BA2121">&#39;a6&#39;</span>: Distance_wText((<span style="color: #666666">4</span>,<span style="color: #666666">5</span>), (<span style="color: #666666">4</span>, <span style="color: #666666">4</span>), t, fontsize),
        <span style="color: #BA2121">&#39;a1&#39;</span>: Distance_wText((<span style="color: #666666">0</span>,<span style="color: #666666">2</span>), (<span style="color: #666666">2</span>, <span style="color: #666666">4.5</span>), t, fontsize),
        <span style="color: #BA2121">&#39;a2&#39;</span>: Distance_wText((<span style="color: #666666">0</span>,<span style="color: #666666">2</span>), (<span style="color: #666666">2</span>, <span style="color: #666666">0</span>), t, fontsize),
        <span style="color: #BA2121">&#39;a3&#39;</span>: Distance_wText((<span style="color: #666666">2</span>,<span style="color: #666666">4.5</span>), (<span style="color: #666666">0</span>, <span style="color: #666666">5.5</span>), t, fontsize),
        <span style="color: #BA2121">&#39;a4&#39;</span>: Distance_wText((<span style="color: #666666">8</span>,<span style="color: #666666">4</span>), (<span style="color: #666666">10</span>, <span style="color: #666666">3</span>), t, fontsize,
                             text_spacing<span style="color: #666666">=-1./60</span>),
        <span style="color: #BA2121">&#39;a5&#39;</span>: Distance_wText((<span style="color: #666666">8</span>,<span style="color: #666666">2</span>), (<span style="color: #666666">10</span>, <span style="color: #666666">1</span>), t, fontsize,
                             text_spacing<span style="color: #666666">=-1./40</span>, alignment<span style="color: #666666">=</span><span style="color: #BA2121">&#39;right&#39;</span>),
        <span style="color: #BA2121">&#39;c1&#39;</span>: Text_wArrow(<span style="color: #BA2121">&#39;text_spacing=-1./60&#39;</span>,
                          (<span style="color: #666666">4</span>, <span style="color: #666666">3.5</span>), (<span style="color: #666666">9</span>, <span style="color: #666666">3.2</span>),
                          fontsize<span style="color: #666666">=10</span>, alignment<span style="color: #666666">=</span><span style="color: #BA2121">&#39;left&#39;</span>),
        <span style="color: #BA2121">&#39;c2&#39;</span>: Text_wArrow(<span style="color: #BA2121">&#39;text_spacing=-1./40, alignment=&quot;right&quot;&#39;</span>,
                          (<span style="color: #666666">4</span>, <span style="color: #666666">0.5</span>), (<span style="color: #666666">9</span>, <span style="color: #666666">1.2</span>),
                          fontsize<span style="color: #666666">=10</span>, alignment<span style="color: #666666">=</span><span style="color: #BA2121">&#39;left&#39;</span>),
        })
    examples<span style="color: #666666">.</span>draw()
    drawing_tool<span style="color: #666666">.</span>display(<span style="color: #BA2121">&#39;Distance_wText and text positioning&#39;</span>)
</pre></div>
<p>
Note the use of <code>Text_wArrow</code> to write an explaining text with an
associated arrow, here used to explain how
the <code>text_spacing</code> and <code>alignment</code> arguments can be used to adjust
the appearance of the text that goes with the distance arrow.

<h2 id="___sec19">Rectangle </h2>

<p>
<center><p><img src="fig-tut/Rectangle.png" align="bottom" width=500></p></center>

<p>
<br />
<br />

<p>
The above figure can be produced by the following code.

<p>

<!-- code=python (!bc pycod) typeset with pygments style "default" -->
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%"><span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">test_Rectangle</span>():
    L <span style="color: #666666">=</span> <span style="color: #666666">3.0</span>
    W <span style="color: #666666">=</span> <span style="color: #666666">4.0</span>

    drawing_tool<span style="color: #666666">.</span>set_coordinate_system(
        xmin<span style="color: #666666">=0</span>, xmax<span style="color: #666666">=2*</span>W, ymin<span style="color: #666666">=-</span>L<span style="color: #666666">/2</span>, ymax<span style="color: #666666">=2*</span>L,
        axis<span style="color: #666666">=</span><span style="color: #008000">True</span>, instruction_file<span style="color: #666666">=</span><span style="color: #BA2121">&#39;tmp_Rectangle.py&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_linecolor(<span style="color: #BA2121">&#39;blue&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_grid(<span style="color: #008000">True</span>)

    xpos <span style="color: #666666">=</span> W<span style="color: #666666">/2</span>
    r <span style="color: #666666">=</span> Rectangle(lower_left_corner<span style="color: #666666">=</span>(xpos,<span style="color: #666666">0</span>), width<span style="color: #666666">=</span>W, height<span style="color: #666666">=</span>L)
    r<span style="color: #666666">.</span>draw()
    r<span style="color: #666666">.</span>draw_dimensions()
    drawing_tool<span style="color: #666666">.</span>display(<span style="color: #BA2121">&#39;Rectangle&#39;</span>)
</pre></div>
<p>
Note that the <code>draw_dimension</code> method adds explanation of dimensions and various
important argument in the construction of a shape. It adapts the annotations
to the geometry of the current shape.

<h2 id="___sec20">Triangle </h2>

<p>
<center><p><img src="fig-tut/Triangle.png" align="bottom" width=500></p></center>

<p>
<br />
<br />

<p>
The code below produces the figure.

<p>

<!-- code=python (!bc pycod) typeset with pygments style "default" -->
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%"><span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">test_Triangle</span>():
    L <span style="color: #666666">=</span> <span style="color: #666666">3.0</span>
    W <span style="color: #666666">=</span> <span style="color: #666666">4.0</span>

    drawing_tool<span style="color: #666666">.</span>set_coordinate_system(
        xmin<span style="color: #666666">=0</span>, xmax<span style="color: #666666">=2*</span>W, ymin<span style="color: #666666">=-</span>L<span style="color: #666666">/2</span>, ymax<span style="color: #666666">=1.2*</span>L,
        axis<span style="color: #666666">=</span><span style="color: #008000">True</span>, instruction_file<span style="color: #666666">=</span><span style="color: #BA2121">&#39;tmp_Triangle.py&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_linecolor(<span style="color: #BA2121">&#39;blue&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_grid(<span style="color: #008000">True</span>)

    xpos <span style="color: #666666">=</span> <span style="color: #666666">1</span>
    t <span style="color: #666666">=</span> Triangle(p1<span style="color: #666666">=</span>(W<span style="color: #666666">/2</span>,<span style="color: #666666">0</span>), p2<span style="color: #666666">=</span>(<span style="color: #666666">3*</span>W<span style="color: #666666">/2</span>,W<span style="color: #666666">/2</span>), p3<span style="color: #666666">=</span>(<span style="color: #666666">4*</span>W<span style="color: #666666">/5.</span>,L))
    t<span style="color: #666666">.</span>draw()
    t<span style="color: #666666">.</span>draw_dimensions()
    drawing_tool<span style="color: #666666">.</span>display(<span style="color: #BA2121">&#39;Triangle&#39;</span>)
</pre></div>
<p>
Here, the <code>draw_dimension</code> method writes the name of the corners at the
position of the corners, which does not always look nice (the present figure
is an example). For a high-quality sketch one would add some spacing
to the location of the p1, p2, and even p3 texts.

<h2 id="___sec21">Arc </h2>

<p>
<center><p><img src="fig-tut/Arc.png" align="bottom" width=400></p></center>

<p>
<br />
<br />

<p>
An arc like the one above is produced by

<p>

<!-- code=python (!bc pycod) typeset with pygments style "default" -->
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%"><span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">test_Arc</span>():
    L <span style="color: #666666">=</span> <span style="color: #666666">4.0</span>
    W <span style="color: #666666">=</span> <span style="color: #666666">4.0</span>

    drawing_tool<span style="color: #666666">.</span>set_coordinate_system(
        xmin<span style="color: #666666">=-</span>W<span style="color: #666666">/2</span>, xmax<span style="color: #666666">=</span>W, ymin<span style="color: #666666">=-</span>L<span style="color: #666666">/2</span>, ymax<span style="color: #666666">=1.5*</span>L,
        axis<span style="color: #666666">=</span><span style="color: #008000">True</span>, instruction_file<span style="color: #666666">=</span><span style="color: #BA2121">&#39;tmp_Arc.py&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_linecolor(<span style="color: #BA2121">&#39;blue&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_grid(<span style="color: #008000">True</span>)

    center <span style="color: #666666">=</span> point(<span style="color: #666666">0</span>,<span style="color: #666666">0</span>)
    radius <span style="color: #666666">=</span> L<span style="color: #666666">/2</span>
    start_angle <span style="color: #666666">=</span> <span style="color: #666666">60</span>
    arc_angle <span style="color: #666666">=</span> <span style="color: #666666">45</span>
    a <span style="color: #666666">=</span> Arc(center, radius, start_angle, arc_angle)
    a<span style="color: #666666">.</span>draw()

    R1 <span style="color: #666666">=</span> <span style="color: #666666">1.25*</span>radius
    R2 <span style="color: #666666">=</span> <span style="color: #666666">1.5*</span>radius
    R <span style="color: #666666">=</span> <span style="color: #666666">2*</span>radius
    a<span style="color: #666666">.</span>dimensions <span style="color: #666666">=</span> {
        <span style="color: #BA2121">&#39;start_angle&#39;</span>:
        Arc_wText(
            <span style="color: #BA2121">&#39;start_angle&#39;</span>, center, R1, start_angle<span style="color: #666666">=0</span>,
            arc_angle<span style="color: #666666">=</span>start_angle, text_spacing<span style="color: #666666">=1/10.</span>),
        <span style="color: #BA2121">&#39;arc_angle&#39;</span>:
        Arc_wText(
            <span style="color: #BA2121">&#39;arc_angle&#39;</span>, center, R2, start_angle<span style="color: #666666">=</span>start_angle,
            arc_angle<span style="color: #666666">=</span>arc_angle, text_spacing<span style="color: #666666">=1/20.</span>),
        <span style="color: #BA2121">&#39;r=0&#39;</span>:
        Line(center, center <span style="color: #666666">+</span>
             point(R<span style="color: #666666">*</span>cos(radians(start_angle)),
                   R<span style="color: #666666">*</span>sin(radians(start_angle)))),
        <span style="color: #BA2121">&#39;r=start_angle&#39;</span>:
        Line(center, center <span style="color: #666666">+</span>
             point(R<span style="color: #666666">*</span>cos(radians(start_angle<span style="color: #666666">+</span>arc_angle)),
                   R<span style="color: #666666">*</span>sin(radians(start_angle<span style="color: #666666">+</span>arc_angle)))),
        <span style="color: #BA2121">&#39;r=start+arc_angle&#39;</span>:
        Line(center, center <span style="color: #666666">+</span>
             point(R, <span style="color: #666666">0</span>))<span style="color: #666666">.</span>set_linestyle(<span style="color: #BA2121">&#39;dashed&#39;</span>),
        <span style="color: #BA2121">&#39;radius&#39;</span>: Distance_wText(center, a(<span style="color: #666666">0</span>), <span style="color: #BA2121">&#39;radius&#39;</span>, text_spacing<span style="color: #666666">=1/40.</span>),
        <span style="color: #BA2121">&#39;center&#39;</span>: Text(<span style="color: #BA2121">&#39;center&#39;</span>, center<span style="color: #666666">-</span>point(radius<span style="color: #666666">/10.</span>, radius<span style="color: #666666">/10.</span>)),
        }
    <span style="color: #008000; font-weight: bold">for</span> dimension <span style="color: #AA22FF; font-weight: bold">in</span> a<span style="color: #666666">.</span>dimensions:
        <span style="color: #008000; font-weight: bold">if</span> dimension<span style="color: #666666">.</span>startswith(<span style="color: #BA2121">&#39;r=&#39;</span>):
            dim <span style="color: #666666">=</span> a<span style="color: #666666">.</span>dimensions[dimension]
            dim<span style="color: #666666">.</span>set_linestyle(<span style="color: #BA2121">&#39;dashed&#39;</span>)
            dim<span style="color: #666666">.</span>set_linewidth(<span style="color: #666666">1</span>)
            dim<span style="color: #666666">.</span>set_linecolor(<span style="color: #BA2121">&#39;black&#39;</span>)

    a<span style="color: #666666">.</span>draw_dimensions()
    drawing_tool<span style="color: #666666">.</span>display(<span style="color: #BA2121">&#39;Arc&#39;</span>)
</pre></div>

<h2 id="___sec22">Spring </h2>

<p>
<center><p><img src="fig-tut/Spring.png" align="bottom" width=800></p></center>

<p>
<br />
<br />

<p>
The code for making these two springs goes like this:

<p>

<!-- code=python (!bc pycod) typeset with pygments style "default" -->
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%"><span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">test_Spring</span>():
    L <span style="color: #666666">=</span> <span style="color: #666666">5.0</span>
    W <span style="color: #666666">=</span> <span style="color: #666666">2.0</span>

    drawing_tool<span style="color: #666666">.</span>set_coordinate_system(
        xmin<span style="color: #666666">=0</span>, xmax<span style="color: #666666">=7*</span>W, ymin<span style="color: #666666">=-</span>L<span style="color: #666666">/2</span>, ymax<span style="color: #666666">=1.5*</span>L,
        axis<span style="color: #666666">=</span><span style="color: #008000">True</span>, instruction_file<span style="color: #666666">=</span><span style="color: #BA2121">&#39;tmp_Spring.py&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_linecolor(<span style="color: #BA2121">&#39;blue&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_grid(<span style="color: #008000">True</span>)

    xpos <span style="color: #666666">=</span> W
    s1 <span style="color: #666666">=</span> Spring((W,<span style="color: #666666">0</span>), L, teeth<span style="color: #666666">=</span><span style="color: #008000">True</span>)
    s1_title <span style="color: #666666">=</span> Text(<span style="color: #BA2121">&#39;Default Spring&#39;</span>,
                    s1<span style="color: #666666">.</span>geometric_features()[<span style="color: #BA2121">&#39;end&#39;</span>] <span style="color: #666666">+</span> point(<span style="color: #666666">0</span>,L<span style="color: #666666">/10</span>))
    s1<span style="color: #666666">.</span>draw()
    s1_title<span style="color: #666666">.</span>draw()
    <span style="color: #408080; font-style: italic">#s1.draw_dimensions()</span>
    xpos <span style="color: #666666">+=</span> <span style="color: #666666">3*</span>W
    s2 <span style="color: #666666">=</span> Spring(start<span style="color: #666666">=</span>(xpos,<span style="color: #666666">0</span>), length<span style="color: #666666">=</span>L, width<span style="color: #666666">=</span>W<span style="color: #666666">/2.</span>,
                bar_length<span style="color: #666666">=</span>L<span style="color: #666666">/6.</span>, teeth<span style="color: #666666">=</span><span style="color: #008000">False</span>)
    s2<span style="color: #666666">.</span>draw()
    s2<span style="color: #666666">.</span>draw_dimensions()
    drawing_tool<span style="color: #666666">.</span>display(<span style="color: #BA2121">&#39;Spring&#39;</span>)
</pre></div>

<h2 id="___sec23">Dashpot </h2>

<p>
<center><p><img src="fig-tut/Dashpot.png" align="bottom" width=600></p></center>

<p>
<br />
<br />

<p>
This dashpot is produced by

<p>

<!-- code=python (!bc pycod) typeset with pygments style "default" -->
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%"><span style="color: #008000; font-weight: bold">def</span> <span style="color: #0000FF">test_Dashpot</span>():
    L <span style="color: #666666">=</span> <span style="color: #666666">5.0</span>
    W <span style="color: #666666">=</span> <span style="color: #666666">2.0</span>
    xpos <span style="color: #666666">=</span> <span style="color: #666666">0</span>

    drawing_tool<span style="color: #666666">.</span>set_coordinate_system(
        xmin<span style="color: #666666">=</span>xpos, xmax<span style="color: #666666">=</span>xpos<span style="color: #666666">+5.5*</span>W, ymin<span style="color: #666666">=-</span>L<span style="color: #666666">/2</span>, ymax<span style="color: #666666">=1.5*</span>L,
        axis<span style="color: #666666">=</span><span style="color: #008000">True</span>, instruction_file<span style="color: #666666">=</span><span style="color: #BA2121">&#39;tmp_Dashpot.py&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_linecolor(<span style="color: #BA2121">&#39;blue&#39;</span>)
    drawing_tool<span style="color: #666666">.</span>set_grid(<span style="color: #008000">True</span>)

    <span style="color: #408080; font-style: italic"># Default (simple) dashpot</span>
    xpos <span style="color: #666666">=</span> <span style="color: #666666">1.5</span>
    d1 <span style="color: #666666">=</span> Dashpot(start<span style="color: #666666">=</span>(xpos,<span style="color: #666666">0</span>), total_length<span style="color: #666666">=</span>L)
    d1_title <span style="color: #666666">=</span> Text(<span style="color: #BA2121">&#39;Dashpot (default)&#39;</span>,
                    d1<span style="color: #666666">.</span>geometric_features()[<span style="color: #BA2121">&#39;end&#39;</span>] <span style="color: #666666">+</span> point(<span style="color: #666666">0</span>,L<span style="color: #666666">/10</span>))
    d1<span style="color: #666666">.</span>draw()
    d1_title<span style="color: #666666">.</span>draw()

    <span style="color: #408080; font-style: italic"># Dashpot for animation with fixed bar_length, dashpot_length and</span>
    <span style="color: #408080; font-style: italic"># prescribed piston_pos</span>
    xpos <span style="color: #666666">+=</span> <span style="color: #666666">2.5*</span>W
    d2 <span style="color: #666666">=</span> Dashpot(start<span style="color: #666666">=</span>(xpos,<span style="color: #666666">0</span>), total_length<span style="color: #666666">=1.2*</span>L, width<span style="color: #666666">=</span>W<span style="color: #666666">/2</span>,
                 bar_length<span style="color: #666666">=</span>W, dashpot_length<span style="color: #666666">=</span>L<span style="color: #666666">/2</span>, piston_pos<span style="color: #666666">=2*</span>W)
    d2<span style="color: #666666">.</span>draw()
    d2<span style="color: #666666">.</span>draw_dimensions()

    drawing_tool<span style="color: #666666">.</span>display(<span style="color: #BA2121">&#39;Dashpot&#39;</span>)
</pre></div>

<h2 id="___sec24">Wavy </h2>

<p>
Looks strange. Fix x axis.

<h2 id="___sec25">Stochastic curves </h2>

<p>
The <code>StochasticWavyCurve</code> object offers three precomputed
graphics that have a random variation:

<p>
<br />
<br />

<p>
<center><p><img src="fig-tut/StochasticWavyCurve.png" align="bottom" width=600></p></center>

<p>
<br />
<br />

<p>
The usage is simple. The construction

<p>

<!-- code=python (!bc pycod) typeset with pygments style "default" -->
<div class="highlight" style="background: #f8f8f8"><pre style="line-height: 125%">curve <span style="color: #666666">=</span> StochasticWavyCurve(curve_no<span style="color: #666666">=1</span>, percentage<span style="color: #666666">=40</span>)
</pre></div>
<p>
picks the second curve (the three are numbered 0, 1, and 2),
and the first 40% of that curve. In case one desires another extent
of the axis, one can just scale the coordinates directly as these
are stored in the arrays <code>curve.x[curve_no]</code> and
<code>curve.y[curve_no]</code>.

<p>
<p>
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