onzd2.f
Go to the documentation of this file.
1 c> \ingroup core
2 c> Function to round a digit to one significant figure (one non zero digit), double precision
3 c>
4 c> Function "onzd" stands for "One Non Zero Digit"
5 c>
6 c> Version 2 operates just like version 1 (onzd()), only the input
7 c> and output will be real*8 values, not real*4.
8 c>
9 c> It takes a Real*8 number as input, and rounds that
10 c> number to the closest number containing only 1 non-zero digit.
11 c> The list of such numbers is infifinite, but contain
12 c> these, in order:
13 c>
14 c> 0.7 , 0.8 , 0.9 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9, 10 , 20 , 30 , etc etc
15 c>
16 c> \param[in] x input value
17 c> \return real*8 rounded value of x to one non zero digit
18 c>
19 c> Examples of input/output are:
20 c>
21 c> 0.000019 => 0.000020
22 c> 0.007432 => 0.007000
23 c> 1.7 => 2.000000
24 c> 9.143 => 9.000000
25 c> 17.4 => 20.000000
26 c> 947.3 => 900.000000
27 c> 987.432 => 1000.000000
28 c> 1014.8 => 1000.000000
29 c> 1502.7 => 2000.000000
30 c>
31  function onzd2(x)
32  implicit none
33  real*8 onzd2,x,y
34  real*8 q,qten
35  integer*4 imag,iq,isign
36
37 c - Function "onzd2" stands for "One Non Zero Digit, version 2"
38
39 c - Version 2 operates just like version 1 (onzd.f), only the input
40 c - and output will be real*8 values, not real*4.
41
42 c - It takes a Real*8 number as input, and rounds that
43 c - number to the closest number containing only 1 non-zero digit.
44 c - The list of such numbers is infifinite, but contain
45 c - these, in order:
46 c - 0.7 , 0.8 , 0.9 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9, 10 , 20 , 30 , etc etc
47 c -
48 c - Examples of input/output are:
49 c - 0.000019 => 0.000020
50 c - 0.007432 => 0.007000
51 c - 1.7 => 2.000000
52 c - 9.143 => 9.000000
53 c - 17.4 => 20.000000
54 c - 947.3 => 900.000000
55 c - 987.432 => 1000.000000
56 c - 1014.8 => 1000.000000
57 c - 1502.7 => 2000.000000
58
59  y = x
60  isign = +1
61  if(x.lt.0)then
62  isign = -1
63  y = -x
64  endif
65
66 c - 1) Determine magnitude of x, in terms of integer exponent of ten
67  imag = floor(dlog10(y))
68
69 c - 1a) Get the multiplier
70  qten = (10.d0**imag)
71
72 c - 2) Get into a range between 0.0 and 10.0
73  q = dble(y) / qten
74
75 c - 3) Round to the closest integer (0 through 10)
76  iq = nint(q)
77
78 c - 4) Scale back to the original size
79  onzd2 = isign * dble(iq) * qten
80
81 c write(6,100)x,imag,qten,q,iq,onzd2
82 c 100 format(f30.15,1x,i10,1x,f30.15,1x,f30.15,1x,i10,1x,f30.15)
83
84  return
85  end
86
real *8 function onzd2(x)
Function to round a digit to one significant figure (one non zero digit), double precision.
Definition: onzd2.f:32