[GRASS-SVN] r37384 - grass/trunk/raster/r.series

[svn_grass at osgeo.org]

Author: helena
Date: 2009-05-22 20:44:37 -0400 (Fri, 22 May 2009)
New Revision: 37384

Modified:
   grass/trunk/raster/r.series/r.series.html
Log:
hint for handling irregular time intervals for regression

Modified: grass/trunk/raster/r.series/r.series.html
===================================================================
--- grass/trunk/raster/r.series/r.series.html	2009-05-22 22:43:38 UTC (rev 37383)
+++ grass/trunk/raster/r.series/r.series.html	2009-05-23 00:44:37 UTC (rev 37384)
@@ -49,6 +49,10 @@
 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>
 
@@ -59,9 +63,15 @@
     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):