GRASS Programmer's Manual  6.4.2(2012)
basic.c
Go to the documentation of this file.
00001 #include <math.h>
00002 #include <grass/arraystats.h>
00003 
00004 
00005 /*provides basic univar stats */
00006 void basic_stats(double *data, int count, struct GASTATS *stats)
00007 {
00008     int i = 1;
00009     double sum = 0, sumsq = 0, sumabs = 0;
00010     double dev = 0, dev2 = 0;
00011 
00012     stats->count = count;
00013     stats->min = data[0];
00014     stats->max = data[count - 1];
00015 
00016     for (i = 0; i < count; i++) {
00017         sum += data[i];
00018         sumabs += fabs(data[i]);
00019         sumsq += data[i] * data[i];
00020     }
00021     stats->sum = sum;
00022     stats->sumabs = sumabs;
00023     stats->sumsq = sumsq;
00024 
00025     stats->mean = stats->sum / stats->count;
00026     stats->meanabs = stats->sumabs / stats->count;
00027     for (i = 0; i < count; i++) {
00028         dev2 = dev2 + (data[i] - stats->mean) * (data[i] - stats->mean);
00029         dev = dev + (data[i] - stats->mean);
00030     }
00031 
00032 
00033     stats->var = (dev2 - (dev * dev / stats->count)) / stats->count;
00034     stats->stdev = sqrt(stats->var);
00035 
00036     return;
00037 }
00038 
00039 
00040 void eqdrt(double vectx[], double vecty[], int i1, int i2, double *vabc)
00041 {
00042     double bn = 0, bd = 0, x1 = 0, y1 = 0;
00043 
00044     vabc[0] = 0;
00045     vabc[1] = 0;
00046     vabc[2] = 0;
00047     if (i1 == 0) {
00048         x1 = 0;
00049         y1 = 0;
00050     }
00051     else {
00052         x1 = vectx[i1];
00053         y1 = vecty[i1];
00054     }
00055     bn = y1 - vecty[i2];
00056     bd = x1 - vectx[i2];
00057     if (bd != 0) {
00058         vabc[1] = bn / bd;
00059         vabc[0] = y1 - vabc[1] * x1;
00060         return;
00061     }
00062     if (bn != 0)
00063         vabc[2] = x1;
00064     else
00065         G_debug(3, "Points are equal\n");
00066     return;
00067 }
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Friends Defines