doc I item #552, was opened at 2007-12-05 02:04 Status: Open Priority: 3 Submitted By: Nikos Alexandris (nikosa) Assigned to: Nobody (None) Summary: Comments upon the "r.regression.line" script. Issue status: None Doc section: raster GRASS version: CVS HEAD Doc timestamp (YYMMDD):
Initial Comment: Some comments upon the "r.regression.line" documentation (and script!) (The formula of a regression line is, as given in the script is: y = a + b*x.) (1) The terminology used in this script is a bit unconventional but makes more or less sense. "a", which is the incept, is called offset and "b", which is the slope, is called gain. --- (2) Among the results printed out after running the script (Line 105: echo "a b R N F medX sdX medY sdY") F is not explained anywhere. Within the script (line 86) it is defined as F= R^2/(1-R^2/tot-2) --- (3) Line 101 prints out: echo " R: sumXY - sumX*sumY/tot" which is actually half of the formula for Pearson's correlation coefficient "r" [ as correctly expressed in line 83: R= (sumXY - sumX*sumY/tot)/((sumsqX - sumX^2/tot)*(sumsqY - sumY^2/tot))^0.5 ] --- (4) Line 103 prints out: echo " medX, medY: Medians" allthough the "mean" is (correctly) used in the script (in lines 84 and 85, mediaX=sumX/tot and mediaY=sumY/tot respectively), it's incorrectly (?) named as "median". --- ---------------------------------------------------------------------- You can respond by visiting: http://wald.intevation.org/tracker/?func=detail&atid=207&aid=552&group_id=21 _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
