Source Code for Module stistools.r_util

 1  from __future__ import division         # confidence high 
 2  import os 
 3  import os.path 
 4  import copy 
 5   
 6 -def expandFileName (filename): 
 7      """Expand environment variable in a file name. 
 8   
 9      If the input file name begins with either a Unix-style or IRAF-style 
10      environment variable (e.g. $lref/name_dqi.fits or lref$name_dqi.fits 
11      respectively), this routine expands the variable and returns a complete 
12      path name for the file. 
13   
14      @param filename:  a file name, possibly including an environment variable 
15      @type filename:  string 
16   
17      @return:  the file name with environment variable expanded 
18      @rtype:  string 
19      """ 
20   
21      n = filename.find ("$") 
22      if n == 0: 
23          if filename != NOT_APPLICABLE: 
24              # Unix-style file name. 
25              filename = os.path.expandvars (filename) 
26      elif n > 0: 
27          # IRAF-style file name. 
28          temp = "$" + filename[0:n] + os.sep + filename[n+1:] 
29          filename = os.path.expandvars (temp) 
30          # If filename contains "//", delete all of them. 
31          double_sep = os.sep + os.sep 
32          filename = filename.replace(double_sep,os.sep) 
33   
34      return filename 
35   
36 -def interpolate (x, values, xp): 
37      """Interpolate. 
38   
39      Linear interpolation is used.  If the specified indpendent variable 
40      value xp is outside the range of the array x, the first (or last) 
41      value in values will be returned. 
42   
43      @param x:  array of independent variable values 
44      @type x:  a sequence object, e.g. an array, int or float 
45   
46      @param values:  array of dependent variable values 
47      @type values:  a sequence object, e.g. an array (not character) 
48   
49      @param xp:  independent variable value at which to interpolate 
50      @type xp:  int or float 
51   
52      @return:  linearly interpolated value 
53      @rtype:  the same type as one element of values 
54      """ 
55   
56      nvalues = len (values) 
57   
58      if nvalues == 1 or xp <= x.item(0): 
59          value = copy.deepcopy (values[0]) 
60      elif xp >= x.item(nvalues-1): 
61          value = copy.deepcopy (values[nvalues-1]) 
62      else: 
63          # search for independent variable values that bracket the specified xp 
64          for i in range (nvalues-1): 
65              x0 = x.item(i) 
66              x1 = x.item(i+1) 
67              if xp >= x0 and xp <= x1: 
68                  if x0 == x1: 
69                      value = copy.deepcopy (values[i]) 
70                  else: 
71                      p = float (x1 - xp) 
72                      q = float (xp - x0) 
73                      value = (p * values[i] + q * values[i+1]) / (p + q) 
74                  break 
75   
76      return value 
77