Dear Elaine,<br><br>I would suggest to start by reading the Biomod Manual, it contains explanations on which functions should be used for generating background pseudo-absences (i.e. artificial absences when no real absences are available). It will explain how to use the "pseudo.abs()" function.<br>
<br>For general information about different methods to generate pseudo-absences, simply search for "pseudo-absences" using <a href="http://scholar.google.com">scholar.google.com</a>, this will bring-up plenty of papers on the topic.<br>
In particular there is this paper "Assessing the effects of pseudo-absences on predictive distribution model performance" by Chefaoui and Lobo (2007, Ecological Modelling) that should be a good start (then you can also look at the references cited in that paper).<br>
<br>Hope this helps,<br>have a nice day,<br><br>Best,<br>Robin Engler<br><br><br><br><br><div class="gmail_quote">On Sat, Jan 16, 2010 at 1:27 AM, elaine kuo <span dir="ltr"><<a href="http://elaine.kuo.tw">elaine.kuo.tw</a>@<a href="http://gmail.com">gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div>Dear, <br> <br> <br>This is Elaine, a postgraduate studying bird distribution in East Asia.<br>
<br>I found your article in Biological Invasion very interesting.<br>However, I do not see the modelling procedure quite clearly.<br>
<br>Concerning BIOMOD application, please kindly share your experience about </div>
<div>how to generate background data for presence-only data.<br>(which software and which function)<br> <br>Thank you very much in advance.<br> </div>
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