[GRASS-SVN] r53742 - in grass/trunk: include/defs lib/stats raster/r.series
svn_grass at osgeo.org
svn_grass at osgeo.org
Fri Nov 9 03:28:03 PST 2012
Author: glynn
Date: 2012-11-09 03:28:03 -0800 (Fri, 09 Nov 2012)
New Revision: 53742
Modified:
grass/trunk/include/defs/stats.h
grass/trunk/lib/stats/c_reg.c
grass/trunk/raster/r.series/main.c
grass/trunk/raster/r.series/r.series.html
Log:
Add t-value for linear regression
Modified: grass/trunk/include/defs/stats.h
===================================================================
--- grass/trunk/include/defs/stats.h 2012-11-08 23:35:44 UTC (rev 53741)
+++ grass/trunk/include/defs/stats.h 2012-11-09 11:28:03 UTC (rev 53742)
@@ -22,6 +22,7 @@
extern stat_func c_reg_m;
extern stat_func c_reg_c;
extern stat_func c_reg_r2;
+extern stat_func c_reg_t;
extern stat_func c_quart1;
extern stat_func c_quart3;
extern stat_func c_perc90;
@@ -42,6 +43,7 @@
extern stat_func_w w_reg_m;
extern stat_func_w w_reg_c;
extern stat_func_w w_reg_r2;
+extern stat_func_w w_reg_t;
extern stat_func_w w_stddev;
extern stat_func_w w_sum;
extern stat_func_w w_var;
Modified: grass/trunk/lib/stats/c_reg.c
===================================================================
--- grass/trunk/lib/stats/c_reg.c 2012-11-08 23:35:44 UTC (rev 53741)
+++ grass/trunk/lib/stats/c_reg.c 2012-11-09 11:28:03 UTC (rev 53742)
@@ -1,15 +1,22 @@
+#include <math.h>
+
#include <grass/gis.h>
#include <grass/raster.h>
-#define REGRESSION_SLOPE 0
-#define REGRESSION_OFFSET 1
-#define REGRESSION_COEFF_DET 2
+enum {
+ REGRESSION_SLOPE = 0,
+ REGRESSION_OFFSET = 1,
+ REGRESSION_COEFF_DET = 2,
+ REGRESSION_T = 3,
+ REGRESSION_P = 4
+};
static void regression(DCELL * result, DCELL * values, int n, int which)
{
DCELL xsum, ysum;
DCELL xbar, ybar;
DCELL numer, denom, denom2;
+ DCELL Rsq;
int count;
int i;
@@ -42,16 +49,16 @@
denom = 0.0;
for (i = 0; i < n; i++)
if (!Rast_is_d_null_value(&values[i]))
- denom += (DCELL) i *i;
-
+ denom += (DCELL) i * i;
denom -= count * xbar * xbar;
- if (which == REGRESSION_COEFF_DET) {
+ if (which >= REGRESSION_COEFF_DET) {
denom2 = 0.0;
for (i = 0; i < n; i++)
if (!Rast_is_d_null_value(&values[i]))
denom2 += values[i] * values[i];
denom2 -= count * ybar * ybar;
+ Rsq = (numer * numer) / (denom * denom2);
}
switch (which) {
@@ -62,8 +69,11 @@
*result = ybar - xbar * numer / denom;
break;
case REGRESSION_COEFF_DET:
- *result = (numer * numer) / (denom * denom2);
+ *result = Rsq;
break;
+ case REGRESSION_T:
+ *result = sqrt(Rsq * (count - 2) / (1 - Rsq));
+ break;
default:
Rast_set_d_null_value(result, 1);
break;
@@ -89,11 +99,17 @@
regression(result, values, n, REGRESSION_COEFF_DET);
}
+void c_reg_t(DCELL * result, DCELL * values, int n, const void *closure)
+{
+ regression(result, values, n, REGRESSION_T);
+}
+
static void regression_w(DCELL * result, DCELL(*values)[2], int n, int which)
{
DCELL xsum, ysum;
DCELL xbar, ybar;
DCELL numer, denom, denom2;
+ DCELL Rsq;
int count;
int i;
@@ -136,6 +152,7 @@
if (!Rast_is_d_null_value(&values[i][0]))
denom2 += values[i][0] * values[i][0] * values[i][1];
denom2 -= count * ybar * ybar;
+ Rsq = (numer * numer) / (denom * denom2);
}
switch (which) {
@@ -146,8 +163,11 @@
*result = ybar - xbar * numer / denom;
break;
case REGRESSION_COEFF_DET:
- *result = (numer * numer) / (denom * denom2);
+ *result = Rsq;
break;
+ case REGRESSION_T:
+ *result = sqrt(Rsq * (count - 2) / (1 - Rsq));
+ break;
default:
Rast_set_d_null_value(result, 1);
break;
@@ -172,3 +192,8 @@
{
regression_w(result, values, n, REGRESSION_COEFF_DET);
}
+
+void w_reg_t(DCELL * result, DCELL(*values)[2], int n, const void *closure)
+{
+ regression_w(result, values, n, REGRESSION_T);
+}
Modified: grass/trunk/raster/r.series/main.c
===================================================================
--- grass/trunk/raster/r.series/main.c 2012-11-08 23:35:44 UTC (rev 53741)
+++ grass/trunk/raster/r.series/main.c 2012-11-09 11:28:03 UTC (rev 53742)
@@ -45,6 +45,7 @@
{c_reg_m, 0, "slope", "linear regression slope"},
{c_reg_c, 0, "offset", "linear regression offset"},
{c_reg_r2, 0, "detcoeff", "linear regression coefficient of determination"},
+ {c_reg_t, 0, "tvalue", "linear regression t-value"},
{c_quart1, 0, "quart1", "first quartile"},
{c_quart3, 0, "quart3", "third quartile"},
{c_perc90, 0, "perc90", "ninetieth percentile"},
Modified: grass/trunk/raster/r.series/r.series.html
===================================================================
--- grass/trunk/raster/r.series/r.series.html 2012-11-08 23:35:44 UTC (rev 53741)
+++ grass/trunk/raster/r.series/r.series.html 2012-11-09 11:28:03 UTC (rev 53742)
@@ -19,6 +19,7 @@
<li>slope: linear regression slope
<li>offset: linear regression offset
<li>detcoeff: linear regression coefficient of determination
+ <li>tvalue: linear regression t-value
<li>min_raster: raster map number with the minimum time-series value
<li>max_raster: raster map number with the maximum time-series value
</ul>
@@ -45,7 +46,7 @@
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.
+<p>Linear regression (slope, offset, coefficient of determination, t-value) 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).
<p>Number of raster maps to be processed is given by the limit of the
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