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<p class="MsoNormal">I would like an opinion please on package gstat and examining anisotropy in variograms.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have a set of atmospheric science variables in a regular grid of 3000 points at 1 km resolution.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<pre>When I use this code for one variable: <o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre><span style="font-family:"Lucida Console";color:blue">plot(variogram(d1$wrfae ~ 1, d1, alpha=c(0, 45, 90, 135)))</span><span style="font-family:"Lucida Console";color:black"><o:p></o:p></span></pre>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I can see the four different directions have different experimental variograms thus exhibiting anisotropy for that variable (as one might expect in an atmospheric data set). I can do the same for another variable of course.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I construct a cross-variogram for two of the variables and plot for anisotropy thus (because this is what I want – the cross-variogram examining spatial correlation):<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">g <- gstat(NULL, id = "ae", form = wrfae ~ 1, data=d1)<o:p></o:p></p>
<p class="MsoNormal">g <- gstat(g, id = "in", form = intensity ~ 1, data=d1)<o:p></o:p></p>
<p class="MsoNormal">xv1.aeVin <- variogram(g, alpha=c(0))<o:p></o:p></p>
<p class="MsoNormal">xv2.aeVin <- variogram(g, alpha=c(45))<o:p></o:p></p>
<p class="MsoNormal">xv3.aeVin <- variogram(g, alpha=c(90))<o:p></o:p></p>
<p class="MsoNormal">xv4.aeVin <- variogram(g, alpha=c(135))<o:p></o:p></p>
<p class="MsoNormal">plot(xv1.aeVin)<o:p></o:p></p>
<p class="MsoNormal">plot(xv2.aeVin)<o:p></o:p></p>
<p class="MsoNormal">plot(xv3.aeVin)<o:p></o:p></p>
<p class="MsoNormal">plot(xv4.aeVin)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">but - I get exactly the same experimental variograms for two variables – and the cross-variogram - for each direction (thus implying isotropy).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If I use: <o:p></o:p></p>
<p class="MsoNormal">g <- gstat(NULL, id = "ae", form = wrfae ~ 1, data=d1)<o:p></o:p></p>
<p class="MsoNormal">g <- gstat(g, id = "in", form = intensity ~ 1, data=d1)<o:p></o:p></p>
<p class="MsoNormal">xv.aeVin <- variogram(g, alpha=c(0, 45, 90, 135))<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">then I can see the anisotropy for the larger varying variable variogram – but the now superimposed graphs contain also the small varying variable variogram – and the cross-variogram – these lines are not distinguishable from the x-axis
in the four plots (thus unreadable for analysis). <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m looking for a single plot set (2 variograms and a cross variogram for a given direction) – can I achieve that with some code amendments to my second set of code above?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Alternatively – can I extent the y axis (semi-variance) in the third set of code above?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If it helps I can add the plots …<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My thanks,<o:p></o:p></p>
<p class="MsoNormal"><b><i><span style="mso-fareast-language:EN-AU">________________________________________________________<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="mso-fareast-language:EN-AU">Michael Hewson
</span></i></b><i><span style="font-size:10.0pt;mso-fareast-language:EN-AU">PhD candidate<o:p></o:p></span></i></p>
<p class="MsoNormal"><span style="font-size:10.0pt;mso-fareast-language:EN-AU"><a href="http://www.gpem.uq.edu.au/crg"><span style="color:blue">Climate Research Group</span></a> |
<a href="http://www.gpem.uq.edu.au/cser"><span style="color:blue">Centre for Spatial Environmental Research</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;mso-fareast-language:EN-AU">The University of Queensland | Brisbane Q 4072 | Australia<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;mso-fareast-language:EN-AU">m.hewson@uq.edu.au |
<b><i>+61 (0)408 379 373<o:p></o:p></i></b></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;mso-fareast-language:EN-AU"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-AU"><img border="0" width="447" height="55" id="Picture_x0020_1" src="cid:image001.jpg@01CD3DA2.E5F11230" alt="Description: ClimateResearchGroupbanner"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-AU"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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