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<div class="moz-cite-prefix">Hello,<br>
<br>
You can try spline interpolation and numerical derivatives on that
spline<br>
<pre style="font-family:Monospaced;font-style:normal;font-size:16.0;"><span style="color:rgb(100,174,100);font-style:italic;">//function for spline interpolation of x-y data</span>
<span style="color:rgb(50,185,185);">deff</span> <span style="color:rgb(74,85,219);">(</span><span style="color:rgb(188,143,143);">'</span><span style="color:rgb(188,143,143);">[yk] = fspline(xx,x,y)</span><span style="color:rgb(188,143,143);">'</span><span style="color:rgb(0,0,0);">,</span> <span style="color:rgb(255,170,0);">...</span>
<span style="color:rgb(188,143,143);">'</span><span style="color:rgb(188,143,143);">yk=interp(xx, x, y, splin(x,y))</span><span style="color:rgb(188,143,143);">'</span><span style="color:rgb(74,85,219);">)</span><span style="color:rgb(0,0,0);">;
</span><span style="color:rgb(100,174,100);font-style:italic;">//</span>
<span style="color:rgb(100,174,100);font-style:italic;">//Use the spline for finding derivatives</span>
<span style="color:rgb(100,174,100);font-style:italic;">//</span>
<span style="color:rgb(0,0,0);">a</span><span style="color:rgb(92,92,92);">=</span><span style="color:rgb(188,143,143);">10</span> <span style="color:rgb(100,174,100);font-style:italic;">//give the point</span>
<span style="color:rgb(174,92,176);text-decoration:underline;">numdiff</span><span style="color:rgb(74,85,219);">(</span><span style="color:rgb(0,0,0);">fspline</span><span style="color:rgb(0,0,0);">,</span><span style="color:rgb(0,0,0);">a</span><span style="color:rgb(74,85,219);">)</span> <span style="color:rgb(100,174,100);font-style:italic;">//find the derivative at the point</span>
<span style="color:rgb(100,174,100);font-style:italic;">//derivatives at the x points</span>
<span style="color:rgb(160,32,240);">for</span> <span style="color:rgb(0,0,0);">i</span><span style="color:rgb(92,92,92);">=</span><span style="color:rgb(188,143,143);">1</span><span style="color:rgb(255,170,0);">:</span><span style="color:rgb(50,185,185);">length</span><span style="color:rgb(74,85,219);">(</span><span style="color:rgb(0,0,0);">x</span><span style="color:rgb(74,85,219);">)</span>
<span style="color:rgb(0,0,0);">dy</span><span style="color:rgb(74,85,219);">(</span><span style="color:rgb(0,0,0);">i</span><span style="color:rgb(74,85,219);">)</span> <span style="color:rgb(92,92,92);">=</span> <span style="color:rgb(174,92,176);text-decoration:underline;">numdiff</span><span style="color:rgb(74,85,219);">(</span><span style="color:rgb(0,0,0);">fspline</span><span style="color:rgb(0,0,0);">,</span><span style="color:rgb(0,0,0);">x</span><span style="color:rgb(74,85,219);">(</span><span style="color:rgb(0,0,0);">i</span><span style="color:rgb(74,85,219);">)</span><span style="color:rgb(74,85,219);">)</span><span style="color:rgb(0,0,0);">;</span>
<span style="color:rgb(50,185,185);">mprintf</span><span style="color:rgb(74,85,219);">(</span><span style="color:rgb(188,143,143);">'</span><span style="color:rgb(188,143,143);">x=%i, dy=%f\n</span><span style="color:rgb(188,143,143);">'</span><span style="color:rgb(0,0,0);">,</span><span style="color:rgb(0,0,0);">x</span><span style="color:rgb(74,85,219);">(</span><span style="color:rgb(0,0,0);">i</span><span style="color:rgb(74,85,219);">)</span><span style="color:rgb(0,0,0);">,</span><span style="color:rgb(0,0,0);">dy</span><span style="color:rgb(74,85,219);">(</span><span style="color:rgb(0,0,0);">i</span><span style="color:rgb(74,85,219);">)</span><span style="color:rgb(74,85,219);">)</span>
<span style="color:rgb(160,32,240);">end</span></pre>
Regards,<br>
Radovan<br>
<br>
On 3/22/2014 7:00 PM, Samuel Enibe wrote:<br>
</div>
<blockquote
cite="mid:CAJKcLoUfEQDNBhqQ8YgTf+-iEkdHmwVCkTrqMQ7qL73S7uhtBA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>
<div>I would like to use the functions <b>derivative</b> or <b>numdiff</b>
to numerically differentiate a tabulated data such as<br>
<br>
x = [0 2 5 20 40 60 80]';//time in minutes <br>
y = [0.0956820 0.0480457 0.0277857 0.0036214 0.0002543
0.0002543 0.0001265]';//values of y<br>
<br>
</div>
May I know the best way to determine dy/dx for the data set.<br>
<br>
</div>
Thank you very much and God bless you<br>
<div>
<div><br clear="all">
<div>
<div>
<div dir="ltr">Samuel Ogbonna Enibe<br>
University of Nigeria, Nsukka, Nigeria<br>
Tel: +2348063646798<br>
Email: <a moz-do-not-send="true"
href="mailto:samuel.enibe@unn.edu.ng"
target="_blank">samuel.enibe@unn.edu.ng</a><br>
<a moz-do-not-send="true"
href="mailto:enibesam@yahoo.com" target="_blank">enibesam@yahoo.com</a></div>
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