1r.neighbors(1) Grass User's Manual r.neighbors(1)
2
6 r.neighbors - Makes each cell category value a function of the cate‐
7 gory values assigned to the cells around it, and stores new cell values
8 in an output raster map layer.
9
11 raster
12
14 r.neighbors
15 r.neighbors help
16 r.neighbors [-aq] input=string output=string method=string size=integer
17 [title="phrase"] [--overwrite]
18 Flags:
20 -a Do not align output with the input
21 -q Run quietly
23 --overwrite
25 Parameters:
27 input=string
28 Name of existing raster file
29 output=string
31 Name of the new raster file
32 method=string
34 Neighborhood operation Options: average,median,mode,minimum,maxi‐
35 mum,stddev,sum,variance,diversity,interspersion
36 size=integer
38 Neighborhood size Options: 1,3,5,7,9,11,13,15,17,19,21,23,25
39 title=
41 Title of the output raster file
42
44 r.neighbors looks at each cell in a raster input file, and examines the
45 values assigned to the cells in some user-defined "neighborhood" around
46 it. It outputs a new raster map layer in which each cell is assigned a
47 value that is some (user-specified) function of the values in that
48 cell's neighborhood. For example, each cell in the output layer might
49 be assigned a value equal to the average of the values appearing in its
50 3 x 3 cell "neighborhood" in the input layer.
51 The program will be run non-interactively if the user specifies program
53 arguments (see OPTIONS) on the command line. Alternately, the user can
54 simply type r.neighbors on the command line, without program arguments.
55 In this case, the user will be prompted for flag settings and parameter
56 values.
57
59 The user must specify the names of the raster map layers to be used for
60 input and output, the method used to analyze neighborhood values (i.e.,
61 the neighborhood function or operation to be performed), and the size
62 of the neighborhood. Optionally, the user can also specify the TITLE
63 to be assigned to the raster map layer output, elect to not align the
64 resolution of the output with that of the input (the -a option), and
65 elect to run r.neighbors quietly (the -q option). These options are
66 described further below.
67 Neighborhood Operation Methods: The neighborhood operators determine
69 what new value a center cell in a neighborhood will have after examin‐
70 ing values inside its neighboring cells. Each cell in a raster map
71 layer becomes the center cell of a neighborhood as the neighborhood
72 window moves from cell to cell throughout the map layer. r.neighbors
73 can perform the following operations:
74 average
76 The average value within the neighborhood. In the following
77 example, the result would be:
78 (7*4 + 6 + 5 + 4*3)/9 = 5.66
79 The result is rounded to the nearest integer (in this case 6).
80 median The value found half-way through a list of the neighborhood's
82 values, when these are ranged in numerical order.
83 mode The most frequently occurring value in the neighborhood.
85 minimum
87 The minimum value within the neighborhood.
88 maximum
90 The maximum value within the neighborhood.
91 Raw Data Operation New Data
92 ---------------- ----------------
93 | 7 | 7 | 5 | | | | |
94 |----|----|----| average |----|----|----|
95 | | 6 | |
96 |----|----|----| |----|----|----|
97 | 7 | 6 | 4 | | | | |
98 |----|----|----| |----|----|----|
99 stddev The statistical standard deviation of values within the neigh‐
102 borhood (rounded to the nearest integer).
103 sum The sum of values within the neighborhood.
105 variance
107 The statistical variance of values within the neighborhood
108 (rounded to the nearest integer).
109 diversity
111 The number of different values within the neighborhood. In the
112 above example, the diversity is 4.
113 interspersion
115 The percentage of cells containing values which differ from the
116 values assigned to the center cell in the neighborhood, plus 1.
117 In the above example, the interspersion is:
118 5/8 * 100 + 1 = 63.5
119 The result is rounded to the nearest integer (in this case 64).
120 ERROR .RE
121 Neighborhood Size: The neighborhood size specifies which cells sur‐
123 rounding any given cell fall into the neighborhood for that cell. The
124 size must be an odd integer. Options are: 1, 3, 5, 7, 9, 11, 13, 15,
125 17, 19, 21, 23, and 25. For example,
126 _ _ _
127 |_|_|_|
128 |_|_|_|
129 |_|_|_|
130 -a If specified, r.neighbors will not align the output raster map
133 layer with that of the input raster map layer. The r.neighbors
134 program works in the current geographic region. It is recom‐
135 mended, but not required, that the resolution of the geographic
136 region be the same as that of the raster map layer. By default,
137 if unspecified, r.neighbors will align these geographic region
138 settings.
139 -q If specified, r.neighbors will run relatively quietly (i.e.,
141 without printing to standard output notes on the program's
142 progress). If unspecified, the program will print messages to
143 standard output by default.
144
146 The r.neighbors program works in the current geographic region with the
147 current mask, if any. It is recommended, but not required, that the
148 resolution of the geographic region be the same as that of the raster
149 map layer. By default, r.neighbors will align these geographic region
150 settings. However, the user can elect to keep original input and out‐
151 put resolutions which are not aligned by specifying this (e.g., using
152 the -a option).
153 r.neighbors copies the GRASS color files associated with the input
155 raster map layer for those output map layers that are based on the
156 neighborhood average, median, mode, minimum, and maximum. Because
157 standard deviation, variance, diversity, and interspersion are indices,
158 rather than direct correspondents to input values, no color files are
159 copied for these map layers. (The user should note that although the
160 color file is copied for averaged neighborhood function output, whether
161 or not the color file makes sense for the output will be dependent on
162 the input data values.)
163
165 g.region
166 r.clump
167 r.mapcalc
168 r.mfilter
169 r.support
170
172 Michael Shapiro, U.S.Army Construction Engineering Research Laboratory
173 Last changed: $Date: 2006/04/13 19:01:37 $
175 Full index
177GRASS 6.2.2 r.neighbors(1)