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<font face="Courier New">Dear All,<br>
<br>
I find that the extrapolation option for interp1 is not thoroughly
documented. In the Arguments section it states, for extrapolation,</font><br>
<br>
<blockquote>(optional) string, or real value defining the yp(j)
components for xp(j) values outside [x1,xn] interval.<br>
</blockquote>
<br>
In the Description section the only string listed is "extrap" which
says:<br>
<br>
<div class="refsection">
<dl>
<dd>
<p class="para"> the extrapolation is performed by the defined
method </p>
</dd>
</dl>
</div>
<font face="Courier New"><br>
But which is the defined method? If one selects the method
"spline" it is suggested to refer to interp(), which has a
specific argument (called out_mode) with several possibilities for
extrapolation. These possibilities aren't accessible from the
interp1() function, so it should be completely clear in its
documantation which one is used.<br>
<br>
Besides, the argument extrapolation is optional but it is not
clear what happens if it is not used. I suppose it is what appears
under "by default", but again it says<br>
<br>
</font><font face="Courier New"> </font>
<div class="refsection">
<dl>
<dd>
<p class="para"> the extrapolation is performed by the defined
method (for spline method) </p>
</dd>
</dl>
</div>
<br>
But, as already mentioned, tha spline method has <font
face="Courier New">more than one extrapolation strategy, which can
be selected from interp but not from interp1.<br>
<br>
Finally, at least for spline it seems to be no difference between
setting the extrapolation argument to "extrap" or not using it.<br>
<br>
Regards,<br>
<br>
Federico Miyara<br>
</font>
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