Source Code for Module lib.dispersion.two_point

 1  ############################################################################### 
 2  #                                                                             # 
 3  # Copyright (C) 2009 Sebastien Morin                                          # 
 4  # Copyright (C) 2013 Edward d'Auvergne                                        # 
 5  #                                                                             # 
 6  # This file is part of the program relax (http://www.nmr-relax.com).          # 
 7  #                                                                             # 
 8  # This program is free software: you can redistribute it and/or modify        # 
 9  # it under the terms of the GNU General Public License as published by        # 
10  # the Free Software Foundation, either version 3 of the License, or           # 
11  # (at your option) any later version.                                         # 
12  #                                                                             # 
13  # This program is distributed in the hope that it will be useful,             # 
14  # but WITHOUT ANY WARRANTY; without even the implied warranty of              # 
15  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               # 
16  # GNU General Public License for more details.                                # 
17  #                                                                             # 
18  # You should have received a copy of the GNU General Public License           # 
19  # along with this program.  If not, see <http://www.gnu.org/licenses/>.       # 
20  #                                                                             # 
21  ############################################################################### 
22   
23  # Module docstring. 
24  """The relaxation dispersion equations.""" 
25   
26  # Python module imports. 
27  from math import log, sqrt 
28   
29   
30 -def calc_two_point_r2eff(relax_time=None, I_ref=None, I=None): 
31      r"""Calculate the R2eff/R1rho value for the fixed relaxation time data. 
32   
33      The formula is:: 
34   
35                    -1         / I1 \  
36          R2eff = ------- * ln | -- | , 
37                  relax_T      \ I0 / 
38   
39      where relax_T is the fixed delay time, I0 is the reference peak intensity when relax_T is zero, and I1 is the peak intensity in a spectrum of interest. 
40   
41   
42      @keyword relax_time:    The fixed relaxation delay time in seconds. 
43      @type relax_time:       float 
44      @keyword I_ref:         The peak intensity in the reference spectrum. 
45      @type I_ref:            float 
46      @keyword I:             The peak intensity of interest. 
47      @type I:                float 
48      """ 
49   
50      # Calculate and return the value (avoiding integer division problems). 
51      return -1.0 / relax_time * log(float(I) / I_ref) 
52   
53   
54 -def calc_two_point_r2eff_err(relax_time=None, I_ref=None, I=None, I_ref_err=None, I_err=None): 
55      r"""Calculate the R2eff/R1rho error for the fixed relaxation time data. 
56   
57      The formula is:: 
58   
59                                  __________________________________ 
60                        1        / / sigma_I1 \ 2     / sigma_I0 \ 2 
61          sigma_R2 = -------    /  | -------- |   +   | -------- | 
62                     relax_T  \/   \ I1(nu1)  /       \    I0    / 
63   
64      where relax_T is the fixed delay time, I0 and sigma_I0 are the reference peak intensity and error when relax_T is zero, and I1 and sigma_I1 are the peak intensity and error in the spectrum of interest. 
65   
66   
67      @keyword relax_time:    The fixed relaxation delay time in seconds. 
68      @type relax_time:       float 
69      @keyword I_ref:         The peak intensity in the reference spectrum. 
70      @type I_ref:            float 
71      @keyword I:             The peak intensity of interest. 
72      @type I:                float 
73      @keyword I_ref_err:     The peak intensity error in the reference spectrum. 
74      @type I_ref_err:        float 
75      @keyword I_err:         The peak intensity error of interest. 
76      @type I_err:            float 
77      """ 
78   
79      # Calculate and return the value (avoiding integer division problems). 
80      return sqrt((I_ref_err / I_ref)**2 + (I_err / I)**2) / relax_time 
81