Convert v.db.univar to Python

(aside: why v.db.univar rather than db.univar?)


git-svn-id: https://svn.osgeo.org/grass/grass/trunk@33596 15284696-431f-4ddb-bdfa-cd5b030d7da7

scripts/v.db.univar/v.db.univar.py

@@ -0,0 +1,201 @@
+#!/usr/bin/env python
+
+############################################################################
+#
+# MODULE:	v.db.univar (formerly called v.univar.sh)
+# AUTHOR(S):	Michael Barton, Arizona State University
+#               Converted to Python by Glynn Clements
+# PURPOSE:	Calculates univariate statistics from a GRASS vector map attribute column.
+#               Based on r.univar.sh by Markus Neteler
+# COPYRIGHT:	(C) 2005, 2007, 2008 by the GRASS Development Team
+#
+#		This program is free software under the GNU General Public
+#		License (>=v2). Read the file COPYING that comes with GRASS
+#		for details.
+#
+#############################################################################
+
+#%Module
+#% description: Calculates univariate statistics on selected table column for a GRASS vector map.
+#% keywords: vector, statistics
+#%End
+#%flag
+#%  key: e
+#%  description: Extended statistics (quartiles and 90th percentile)
+#%END
+#%option
+#% key: table
+#% type: string
+#% gisprompt: old,vector,vector
+#% description: Name of data table
+#% required : yes
+#%End
+#%option
+#% key: column
+#% type: string
+#% description: Column on which to calculate statistics (must be numeric)
+#% required : yes
+#%end
+#%option
+#% key: database
+#% type: string
+#% description: Database/directory for table
+#% required : no
+#%end
+#%option
+#% key: driver
+#% type: string
+#% description: Database driver
+#% required : no
+#%end
+#%option
+#% key: where
+#% type: string
+#% description: WHERE conditions of SQL statement without 'where' keyword
+#% required : no
+#%end
+
+import sys
+import os
+import atexit
+import math
+import grass
+
+def cleanup():
+    for ext in ['', '.sort']:
+	grass.try_remove(tmp + ext)
+
+def sortfile(infile, outfile):
+    inf = file(infile, 'r')
+    outf = file(outfile, 'w')
+
+    if grass.find_program('sort', ['-n']):
+	grass.run_command('sort', flags = 'n', stdin = inf, stdout = outf)
+    else:
+	# FIXME: we need a large-file sorting function
+	grass.warning("'sort' not found: sorting in memory")
+	lines = inf.readlines()
+	for i in range(len(lines)):
+	    lines[i] = float(lines[i].rstrip('\r\n'))
+	lines.sort()
+	for line in lines:
+	    outf.write(str(line) + '\n')
+
+    inf.close()
+    outf.close()
+
+def main():
+    global tmp
+    tmp = grass.tempfile()
+
+    extend = flags['e']
+    table = options['table']
+    column = options['column']
+    database = options['database']
+    driver = options['driver']
+    where = options['where']
+
+    grass.message("Calculation for column <%s> of table <%s>..." % (column, table))
+    grass.message("Reading column values...")
+
+    sql = "SELECT %s FROM %s" % (column, table)
+    if where:
+	sql += " WHERE " + where
+
+    if not database:
+	database = None
+
+    if not driver:
+	driver = None
+
+    tmpf = file(tmp, 'w')
+    grass.run_command('db.select', flags = 'c', table = table,
+		      database = database, driver = driver, sql = sql,
+		      stdout = tmpf)
+    tmpf.close()
+
+    # check if result is empty
+    tmpf = file(tmp)
+    if tmpf.read(1) == '':
+	grass.fatal("Table <%s> contains no data.", table)
+    tmpf.close()
+
+    # calculate statistics
+    grass.message("Calculating statistics...")
+
+    N = 0
+    sum = 0.0
+    sum2 = 0.0
+    sum3 = 0.0
+    minv = 1e300
+    maxv = -1e300
+
+    tmpf = file(tmp)
+    for line in tmpf:
+	x = float(line.rstrip('\r\n'))
+	N += 1
+	sum += x
+	sum2 += x * x
+	sum3 += abs(x)
+	maxv = max(maxv, x)
+	minv = min(minv, x)
+    tmpf.close()
+
+    if N <= 0:
+	grass.fatal("No non-null values found")
+
+    print ""
+    print "Number of values:", N
+    print "Minimum:", minv
+    print "Maximum:", maxv
+    print "Range:", maxv - minv
+    print "-----"
+    print "Mean:", sum/N
+    print "Arithmetic mean of absolute values:", sum3/N
+    print "Variance:", (sum2 - sum*sum/N)/N
+    print "Standard deviation:", math.sqrt((sum2 - sum*sum/N)/N)
+    print "Coefficient of variation:", (math.sqrt((sum2 - sum*sum/N)/N))/(math.sqrt(sum*sum)/N)
+    print "-----"
+
+    if not extend:
+	return
+
+    #preparations:
+    sortfile(tmp, tmp + ".sort")
+
+    number = N
+    odd = N % 2
+    eostr = ['even','odd'][odd]
+
+    q25pos = round(N * 0.25)
+    q50apos = round(N * 0.50)
+    q50bpos = q50apos + (1 - odd)
+    q75pos = round(N * 0.75)
+    q90pos = round(N * 0.90)
+
+    inf = file(tmp + ".sort")
+    l = 1
+    for line in inf:
+	if l == q25pos:
+	    q25 = float(line.rstrip('\r\n'))
+	if l == q50apos:
+	    q50a = float(line.rstrip('\r\n'))
+	if l == q50bpos:
+	    q50b = float(line.rstrip('\r\n'))
+	if l == q75pos:
+	    q75 = float(line.rstrip('\r\n'))
+	if l == q90pos:
+	    q90 = float(line.rstrip('\r\n'))
+	l += 1
+
+    q50 = (q50a + q50b) / 2
+
+    print "1st Quartile: %f" % q25
+    print "Median (%s N): %f" % (eostr, q50)
+    print "3rd Quartile: %f" % q75
+    print "90th Percentile: %f" % q90
+
+if __name__ == "__main__":
+    options, flags = grass.parser()
+    atexit.register(cleanup)
+    main()