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<p class="MsoNormal">Hello all<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have found that use of the ‘pow’ function causes executables created by ADMB to crash when the first argument is zero, i.e. when a calculation of 0^x is attempted.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In my template files, data relating to a time variable are read into a dvar_vector and (within a loop) each element of this vector is then raised to the power of a model parameter. The time variable is positive in most cases, but occasionally
takes the value of zero, leading to the problem described.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Using the standard mode for ADMB, I have overcome this problem by defining the following function to replace ‘pow’:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><<< >>><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">GLOBALS_SECTION<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> #include <admodel.h><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> dvariable pow2(const dvariable & time, const dvariable & T)<o:p></o:p></p>
<p class="MsoNormal"> {<o:p></o:p></p>
<p class="MsoNormal"> if(time==0)<o:p></o:p></p>
<p class="MsoNormal"> return 0;<o:p></o:p></p>
<p class="MsoNormal"> else return pow(time,T);<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><<< >>><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I would now like to implement a similar solution for the random effects mode of ADMB, but have so far been unsuccessful in my attempts, with a large number of error messages on compilation. I think that my problem lies in the fact that
I do not really understand how to define and manipulate df1b2variable objects.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If anyone can offer a solution or any advice regarding this problem, I would be very grateful.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best wishes<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Oliver<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:EN-GB">Oliver Stirrup<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:EN-GB">PhD Student<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:EN-GB">MRC Clinical Trials Unit at UCL<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:EN-GB">Institute of Clinical Trials & Methodology<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:EN-GB">London UK<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:EN-GB">e-mail:
<a href="oliver.stirrup.13@ucl.ac.uk"><span style="color:blue">oliver.stirrup.13@ucl.ac.uk</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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