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What do you mean by "<span style="color: rgb(74, 85, 219);">it
doesn't work.</span>" error message?, unexpected results?<br>
<br>
I was not able to run it because g R DeltaP and B are undefined.<br>
<br>
<br>
Serge Steer<br>
INRIA<br>
<br>
Le 21/07/2011 11:25, arnaud dujeu a écrit :
<blockquote cite="mid:SNT112-W13E300616AF6F3CDFDF1A1884F0@phx.gbl"
type="cite">
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Hi,
<div><br>
</div>
<div>I've got a problem to solve a non linear differential
equation, which is :</div>
<div><br>
</div>
<div>y1'=A*(1-sin(y2))/(pi/2-y2)-B*y1^2</div>
<div>y2'=y1</div>
<div><br>
</div>
<div><br>
</div>
<div>I'm using ode : </div>
<div><br>
</div>
<div>
<pre style="font-family: Monospaced; font-style: normal; font-size: 14px;"><span style="color: rgb(176, 24, 19);">function</span> <span style="color: rgb(74, 85, 219);">[</span><span style="color: rgb(131, 67, 16); font-weight: bold;">Xprime</span><span style="color: rgb(74, 85, 219);">]</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(0, 0, 0); text-decoration: underline;">VanDerPol</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(131, 67, 16); font-weight: bold;">t</span><span style="color: rgb(0, 0, 0);">, </span><span style="color: rgb(131, 67, 16); font-weight: bold;">X</span><span style="color: rgb(74, 85, 219);">)</span>
<span style="color: rgb(131, 67, 16); font-weight: bold;">Xprime</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(74, 85, 219);">)</span> <span style="color: rgb(92, 92, 92);">=</span> <span style="color: rgb(131, 67, 16); font-weight: bold;">X</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">2</span><span style="color: rgb(74, 85, 219);">)</span>
<span style="color: rgb(131, 67, 16); font-weight: bold;">Xprime</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">2</span><span style="color: rgb(74, 85, 219);">)</span> <span style="color: rgb(92, 92, 92);">=</span> <span style="color: rgb(0, 0, 0);">g</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(0, 0, 0);">R</span><span style="color: rgb(92, 92, 92);">*</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(92, 92, 92);">-</span><span style="color: rgb(50, 185, 185);">sin</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(131, 67, 16); font-weight: bold;">X</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span><span s
tyle="color: rgb(92, 92, 92);">/</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(218, 112, 214);">%pi</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(188, 143, 143);">2</span><span style="color: rgb(92, 92, 92);">-</span><span style="color: rgb(131, 67, 16); font-weight: bold;">X</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(92, 92, 92);">-</span><span style="color: rgb(0, 0, 0);">deltaP</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(0, 0, 0);">B</span><span style="color: rgb(92, 92, 92);">*</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(218, 112, 214);">%pi</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(188, 143, 14
3);">2</span><span style="color: rgb(92, 92, 92);">-</span><span style="color: rgb(131, 67, 16); font-weight: bold;">X</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span>
<span style="color: rgb(176, 24, 19);">endfunction</span>
<span style="color: rgb(0, 0, 0);">t</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(174, 92, 176); text-decoration: underline;">linspace</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">0</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">4</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">3000</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(0, 0, 0);">;</span> <span style="color: rgb(0, 0, 0);">X0</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(74, 85, 219);">[</span><span style="color: rgb(188, 143, 143);">85</span><span style="color: rgb(92, 92, 92);">*</span><span style="color: rgb(218, 112, 214);">%pi</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(188, 143, 143);">180</span><span style="color: rgb(0, 0, 0);">;</span><span style="color:
rgb(188, 143, 143);">0</span><span style="color: rgb(74, 85, 219);">]</span><span style="color: rgb(0, 0, 0);">;</span>
<span style="color: rgb(74, 85, 219);">[</span><span style="color: rgb(0, 0, 0);">u</span><span style="color: rgb(74, 85, 219);">]</span><span style="color: rgb(92, 92, 92);">=</span><span style="color: rgb(50, 185, 185);">ode</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(0, 0, 0);">X0</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">0</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(0, 0, 0);">t</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(0, 0, 0); text-decoration: underline;">VanDerPol</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(0, 0, 0);">;</span>
<span style="color: rgb(174, 92, 176); text-decoration: underline;">plot</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(0, 0, 0);">t</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(0, 0, 0);">u</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">1</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(255, 170, 0);">:</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(92, 92, 92);">*</span><span style="color: rgb(188, 143, 143);">180</span><span style="color: rgb(92, 92, 92);">/</span><span style="color: rgb(218, 112, 214);">%pi</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(188, 143, 143);">r</span><span style="color: rgb(188, 143, 143);">'</span><span style="color: rgb(74, 85, 219);">)</span>
<span style="color: rgb(174, 92, 176); text-decoration: underline;">plot</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(0, 0, 0);">t</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(0, 0, 0);">R</span><span style="color: rgb(92, 92, 92);">*</span><span style="color: rgb(0, 0, 0);">u</span><span style="color: rgb(74, 85, 219);">(</span><span style="color: rgb(188, 143, 143);">2</span><span style="color: rgb(0, 0, 0);">,</span><span style="color: rgb(255, 170, 0);">:</span><span style="color: rgb(74, 85, 219);">)</span><span style="color: rgb(74, 85, 219);">)</span></pre>
<pre style="font-family: Monospaced; font-style: normal; font-size: 14px;"><span style="color: rgb(74, 85, 219);">
</span></pre>
<pre style="font-family: Monospaced; font-style: normal; font-size: 14px;"><span style="color: rgb(74, 85, 219);">
</span></pre>
<pre style="font-family: Monospaced; font-style: normal; font-size: 14px;"><span style="color: rgb(74, 85, 219);">but it doesn't work.</span></pre>
<pre style="font-family: Monospaced; font-style: normal; font-size: 14px;"><font class="Apple-style-span" color="#4a55db">
</font></pre>
<pre style="font-family: Monospaced; font-style: normal; font-size: 14px;"><font class="Apple-style-span" color="#4a55db">Do you know why?</font></pre>
<pre style="font-family: Monospaced; font-style: normal; font-size: 14px;"><font class="Apple-style-span" color="#4a55db">
</font></pre>
<pre style="font-family: Monospaced; font-style: normal; font-size: 14px;"><font class="Apple-style-span" color="#4a55db">Best regards.</font></pre>
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