1r.average(1) Grass User's Manual r.average(1)
2
6 r.average - Finds the average of values in a cover map within areas
7 assigned the same category value in a user-specified base map.
8
10 raster
11
13 r.average
14 r.average help
15 r.average [-c] base=name cover=name output=name [--overwrite]
16 Flags:
18 -c cover values extracted from the category labels of the cover map
19 --overwrite
21 Parameters:
23 base=name
24 Name of base raster map
25 cover=name
27 Name of cover raster map
28 output=name
30 Name for output raster map
31
33 r.average calculates the average value of data contained in a cover
34 raster map layer for areas assigned the same category value in the
35 user-specified base raster map layer. These averaged values are stored
36 in the category labels file associated with a new output map layer.
37 The values to be averaged are taken from a user-specified cover map.
38 The category values for the cover map will be averaged, unless the -c
39 flag is set. If the -c flag is set, the values that appear in the cat‐
40 egory labels file for the cover map will be averaged instead (see exam‐
41 ple below).
42 The output map is actually a reclass of the base map (see r.reclass),
44 and will have exactly the same category values as the base map. The
45 averaged values computed by r.average are stored in the output map's
46 category labels file. The base= map is an existing raster map layer in
47 the user's current mapset search path. For each group of cells
48 assigned the same category value in the base map, the values assigned
49 these cells in the cover map will be averaged. The cover map is n
50 existing raster map layer containing the values (in the form of cell
51 category values or cell category labels) to be averaged within each
52 category of the base map.
53
55 Assume that farms is a map with 7 farms (i.e., 7 categories), and that
56 soils.Kfactor is a map of soil K factor values with the following cate‐
57 gory file:
58 cat cat
59 value label
60 0 no soil data
61 1 .10
62 2 .15
63 3 .17
64 4 .20
65 5 .24
66 6 .28
67 7 .32
68 8 .37
69 9 .43
70 Then
71 r.average -c base=farms cover=soils.Kfactor output=K.by.farm
73 will compute the average soil K factor for each farm, and store the
75 result in the output map K.by.farm, which will be a reclass of farms
76 with category labels as follows (example only):
77 cat cat
78 value label
79 1 .1023
80 2 .1532
81 3 .172
82 4 .3872
83 5 .003
84 6 .28
85 7 .2345
86
89 The -c option requires that the category label for each category in the
90 cover map be a valid number, integer, or decimal. To be exact, if the
91 first item in the label is numeric, then that value is used. Otherwise,
92 zero is used. The following table covers all possible cases:
93 category value
96 label used by -c
97 ______________________
98 .12 .12
99 .80 KF .8
100 no data 0
101 (This flag is very similar to the @ operator in r.mapcalc, and the user
104 is encouraged to read the manual entry for r.mapcalc to see how it
105 works there.)
106 The user should use the results of r.average with care. Since this
108 utility assigns a value to each cell which is based on global informa‐
109 tion (i.e., information at spatial locations other than just the loca‐
110 tion of the cell itself), the resultant map layer is only valid if the
111 geographic region and mask settings are the same as they were at the
112 time that the result map was created.
113 Results are affected by the current region settings and mask.
115
117 g.region, r.cats, r.clump, r.describe, r.mapcalc, r.mfilter, r.mode,
118 r.neighbors, r.reclass, r.stats
119
121 Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
122 Last changed: $Date: 2006/04/13 19:01:37 $
124 Full index
126GRASS 6.2.2 r.average(1)