GRASS GIS 8 Programmer's Manual
8.5.0dev(2024)-8828094037
c_means.c
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/*!
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\file cluster/c_means.c
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\brief Cluster library - Means value
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(C) 2001-2009 by the GRASS Development Team
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This program is free software under the GNU General Public License
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(>=v2). Read the file COPYING that comes with GRASS for details.
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\author Original author CERL
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*/
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#include <math.h>
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#include <
grass/cluster.h
>
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/*!
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\brief Calculate means value
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\param C pointer to Cluster structure
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\return 0
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*/
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int
I_cluster_means
(
struct
Cluster
*C)
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{
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int
band;
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int
class
;
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double
m, v;
/* m=mean, v=variance then std dev */
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double
s;
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G_debug
(3,
"I_cluster_means(nbands=%d,nclasses=%d)"
, C->
nbands
,
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C->
nclasses
);
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for
(band = 0; band < C->
nbands
; band++) {
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s = C->
band_sum
[band];
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m = s / C->
npoints
;
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v = C->
band_sum2
[band] - s * m;
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v = sqrt(v / (C->
npoints
- 1));
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for
(
class
= 0;
class
< C->nclasses;
class
++)
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C->
mean
[band][class] = m;
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if
(C->
nclasses
> 1)
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for (
class
= 0;
class
< C->nclasses;
class
++)
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C->
mean
[band][class] +=
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((2.0 *
class
) / (C->
nclasses
- 1) - 1.0) * v;
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}
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return
0;
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}
I_cluster_means
int I_cluster_means(struct Cluster *C)
Calculate means value.
Definition:
c_means.c:24
cluster.h
G_debug
int G_debug(int, const char *,...) __attribute__((format(printf
mean
float mean(IClass_statistics *statistics, int band)
Helper function for computing mean.
Definition:
iclass_statistics.c:369
Cluster
Definition:
cluster.h:7
Cluster::npoints
int npoints
Definition:
cluster.h:9
Cluster::band_sum2
double * band_sum2
Definition:
cluster.h:14
Cluster::nclasses
int nclasses
Definition:
cluster.h:26
Cluster::band_sum
double * band_sum
Definition:
cluster.h:13
Cluster::nbands
int nbands
Definition:
cluster.h:8
lib
cluster
c_means.c
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