[GRASS-SVN] r37391 - grass/branches/develbranch_6/raster/r.series

[svn_grass at osgeo.org]

Author: neteler
Date: 2009-05-23 04:20:59 -0400 (Sat, 23 May 2009)
New Revision: 37391

Modified:
   grass/branches/develbranch_6/raster/r.series/description.html
Log:
hint for handling irregular time intervals for regression; example fixes

Modified: grass/branches/develbranch_6/raster/r.series/description.html
===================================================================
--- grass/branches/develbranch_6/raster/r.series/description.html	2009-05-23 08:18:51 UTC (rev 37390)
+++ grass/branches/develbranch_6/raster/r.series/description.html	2009-05-23 08:20:59 UTC (rev 37391)
@@ -46,22 +46,33 @@
 The <em>range</em> parameter can be set to <em>low,high</em> thresholds:
 values outside of this range are treated as NULL (i.e., they will be
 ignored by most aggregates, or will cause the result to be NULL if -n is given).
-The <em>low,high</em> thresholds are floating point, so use <em>-inf</em> or 
+The <em>low,high</em> thresholds are floating point, so use <em>-inf</em> or
 <em>inf</em> for a single threshold (e.g., <em>range=0,inf</em> to ignore
 negative values, or <em>range=-inf,-200.4</em> to ignore values above -200.4).
+<p>
+Linear regression (slope, offset, coefficient of determination) assumes equal time intervals.
+If the data have irregular time intervals, NULL raster maps can be inserted into time series
+to make time intervals equal (see example).
 
 <h2>EXAMPLES</h2>
 
 Using <em>r.series</em> with wildcards:
 <br>
 <div class="code"><pre>
-r.series input="`g.mlist pattern='insitu_data.*' sep=,`"
-    output=insitu_data.stddev method=stddev
+r.series input="`g.mlist pattern='insitu_data.*' sep=,`" \
+         output=insitu_data.stddev method=stddev
 </pre></div>
 <p>
-
-Note the <em>g.mlist</em> script also supports regular expressions for 
+Note the <em>g.mlist</em> script also supports regular expressions for
 selecting map names.
+<p>
+Using <em>r.series</em> with NULL raster maps:
+<br>
+<div class="code"><pre>
+r.mapcalc "dummy = null()"
+r.series in=map2001,map2002,dummy,dummy,map2005,map2006,dummy,map2008 \
+         out=res_slope,res_offset,res_coeff meth=slope,offset,detcoeff
+</pre></div>
 
 <p>
 Example for multiple aggregates to be computed in one run (3 resulting aggregates from two input maps):