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rowmedian.c File Reference

Computes statistical measures such as median, percentiles, average, and middle values for arrays. More...

#include "mdb.h"

Go to the source code of this file.

Functions

long find_median (double *value, double *x, long n)
 Finds the median value of an array of doubles and returns the index of the median.
 
long find_percentile (double *value, double *x, long n, double percentile)
 Finds a specific percentile of an array of doubles and returns the index of the percentile.
 
long find_median_of_row (double *value, double **x, long index, long n)
 Finds the median value of a specific row in a 2D array of doubles and returns the index of the median.
 
long find_average (double *value, double *data, long n)
 Finds the average of an array of doubles and returns the index of the element closest to the average.
 
long find_middle (double *value, double *data, long n)
 Finds the middle value between the minimum and maximum of an array of doubles and returns the index of the closest element.
 

Detailed Description

Computes statistical measures such as median, percentiles, average, and middle values for arrays.

This file contains functions to compute the median, specific percentiles, the average, and the middle value of datasets. It also includes functions to compute these statistics for specific rows in a 2D array. These functions return the index of the closest point to the computed statistic. Requires libsort.a routines.

See also: median.c (doesn't require libsort.a, but doesn't return index).

Copyright
  • (c) 2002 The University of Chicago, as Operator of Argonne National Laboratory.
  • (c) 2002 The Regents of the University of California, as Operator of Los Alamos National Laboratory.
License
This file is distributed under the terms of the Software License Agreement found in the file LICENSE included with this distribution.
Author
M. Borland, C. Saunders, R. Soliday

Definition in file rowmedian.c.

Function Documentation

◆ find_average()

long find_average ( double * value,
double * data,
long n )

Finds the average of an array of doubles and returns the index of the element closest to the average.

Parameters
valuePointer to store the computed average value.
dataPointer to the array of doubles.
nNumber of elements in the array.
Returns
Returns the index of the element closest to the average on success, -1 on failure.

Definition at line 142 of file rowmedian.c.

142 {
143 double sum, min_dist, dist;
144 long i, i_best;
145
146 if (n <= 0)
147 return (-1);
148
149 for (i = sum = 0; i < n; i++)
150 sum += data[i];
151 sum /= n;
152
153 min_dist = DBL_MAX;
154 i_best = -1;
155 for (i = 0; i < n; i++)
156 if ((dist = fabs(data[i] - sum)) < min_dist) {
157 min_dist = dist;
158 i_best = i;
159 }
160 *value = sum;
161 return (i_best);
162}

◆ find_median()

long find_median ( double * value,
double * x,
long n )

Finds the median value of an array of doubles and returns the index of the median.

Parameters
valuePointer to store the computed median value.
xPointer to the array of doubles.
nNumber of elements in the array.
Returns
Returns the index of the median element on success, -1 on failure.

Definition at line 32 of file rowmedian.c.

32 {
33 static double **data = NULL;
34 static long last_n = 0;
35 long i;
36
37 if (n <= 0)
38 return (-1);
39 if (n > last_n) {
40 if (data)
41 free_zarray_2d((void **)data, last_n, 2);
42 data = (double **)zarray_2d(sizeof(**data), n, 2);
43 last_n = n;
44 }
45
46 for (i = 0; i < n; i++) {
47 data[i][0] = x[i];
48 data[i][1] = i;
49 }
50 set_up_row_sort(0, 2, sizeof(**data), double_cmpasc);
51 qsort((void *)data, n, sizeof(*data), row_compare);
52
53 *value = data[n / 2][0];
54 i = data[n / 2][1];
55
56 return (i);
57}
zarray_2d
void ** zarray_2d(uint64_t size, uint64_t n1, uint64_t n2)
Allocates a 2D array with specified dimensions.
Definition array.c:93
free_zarray_2d
int free_zarray_2d(void **array, uint64_t n1, uint64_t n2)
Frees a 2D array and its associated memory.
Definition array.c:155
set_up_row_sort
void set_up_row_sort(int sort_by_column, size_t n_columns, size_t element_size, int(*compare)(const void *a, const void *b))
Set up parameters for row-based sorting.
Definition sortfunctions.c:241
double_cmpasc
int double_cmpasc(const void *a, const void *b)
Compare two doubles in ascending order.
Definition sortfunctions.c:27
row_compare
int row_compare(const void *av, const void *bv)
Compare two rows based on the previously set sorting parameters.
Definition sortfunctions.c:262

◆ find_median_of_row()

long find_median_of_row ( double * value,
double ** x,
long index,
long n )

Finds the median value of a specific row in a 2D array of doubles and returns the index of the median.

Parameters
valuePointer to store the computed median value.
xPointer to the 2D array of doubles.
indexThe row index for which the median is to be computed.
nNumber of elements in the row.
Returns
Returns the index of the median element in the specified row on success, -1 on failure.

Definition at line 106 of file rowmedian.c.

106 {
107 static double **data = NULL;
108 static long last_n = 0;
109 long i;
110
111 if (index < 0 && n <= 0)
112 return (-1);
113
114 if (n > last_n) {
115 if (data)
116 free_zarray_2d((void **)data, last_n, 2);
117 data = (double **)zarray_2d(sizeof(**data), n, 2);
118 last_n = n;
119 }
120
121 for (i = 0; i < n; i++) {
122 data[i][0] = x[i][index];
123 data[i][1] = i;
124 }
125 set_up_row_sort(0, 2, sizeof(**data), double_cmpasc);
126 qsort((void *)data, n, sizeof(*data), row_compare);
127
128 *value = data[n / 2][0];
129 i = data[n / 2][1];
130
131 return (i);
132}

◆ find_middle()

long find_middle ( double * value,
double * data,
long n )

Finds the middle value between the minimum and maximum of an array of doubles and returns the index of the closest element.

Parameters
valuePointer to store the computed middle value.
dataPointer to the array of doubles.
nNumber of elements in the array.
Returns
Returns the index of the element closest to the middle value on success, -1 on failure.

Definition at line 172 of file rowmedian.c.

172 {
173 double target, min_dist, dist, min, max;
174 long i, i_best;
175
176 if (n <= 0)
177 return (-1);
178
179 if (!find_min_max(&min, &max, data, n))
180 return (-1);
181 target = (min + max) / 2;
182
183 min_dist = DBL_MAX;
184 i_best = -1;
185 for (i = 0; i < n; i++)
186 if ((dist = fabs(data[i] - target)) < min_dist) {
187 min_dist = dist;
188 i_best = i;
189 }
190 *value = target;
191 return (i_best);
192}
find_min_max
int find_min_max(double *min, double *max, double *list, int64_t n)
Finds the minimum and maximum values in a list of doubles.
Definition findMinMax.c:33

◆ find_percentile()

long find_percentile ( double * value,
double * x,
long n,
double percentile )

Finds a specific percentile of an array of doubles and returns the index of the percentile.

Parameters
valuePointer to store the computed percentile value.
xPointer to the array of doubles.
nNumber of elements in the array.
percentileThe desired percentile to compute (0-100).
Returns
Returns the index of the percentile element on success, -1 on failure.

Definition at line 68 of file rowmedian.c.

68 {
69 static double **data = NULL;
70 static long last_n = 0;
71 long i;
72
73 if (n <= 0)
74 return (-1);
75 if (percentile < 0 || percentile > 100)
76 return -1;
77 if (n > last_n) {
78 if (data)
79 free_zarray_2d((void **)data, last_n, 2);
80 data = (double **)zarray_2d(sizeof(**data), n, 2);
81 last_n = n;
82 }
83
84 for (i = 0; i < n; i++) {
85 data[i][0] = x[i];
86 data[i][1] = i;
87 }
88 set_up_row_sort(0, 2, sizeof(**data), double_cmpasc);
89 qsort((void *)data, n, sizeof(*data), row_compare);
90
91 *value = data[(long)((n - 1) * (percentile / 100.0))][0];
92 i = data[(long)((n - 1) * (percentile / 100.0))][1];
93
94 return (i);
95}
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