source: sasview/calculator/slit_length_calculator.py @ 6137b150

ESS_GUIESS_GUI_DocsESS_GUI_batch_fittingESS_GUI_bumps_abstractionESS_GUI_iss1116ESS_GUI_iss879ESS_GUI_iss959ESS_GUI_openclESS_GUI_orderingESS_GUI_sync_sascalccostrafo411magnetic_scattrelease-4.1.1release-4.1.2release-4.2.2release_4.0.1ticket-1009ticket-1094-headlessticket-1242-2d-resolutionticket-1243ticket-1249ticket885unittest-saveload
Last change on this file since 6137b150 was 69fee24, checked in by Gervaise Alina <gervyh@…>, 14 years ago

working on documentation

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Line 
1"""
2This module is a small tool to allow user to quickly
3determine the slit length value of data.
4"""
5from numpy import *
6
7class SlitlengthCalculator(object):
8    """
9    compute slit length from SAXSess beam profile (1st col. Q , 2nd col. I ,
10    and 3rd col. dI.: don't need the 3rd)
11    """
12    def __init__(self):
13       
14        # x data
15        self.x = None
16        # y data
17        self.y = None
18        #default slit length
19        self.slit_length = 0.0
20       
21        # The unit is unknown from SAXSess profile:
22        # It seems 1/nm but it could be not fixed,
23        # so users should be notified to determine the unit by themselves.
24        self.slit_length_unit = "unknown"
25   
26    def set_data(self, x=None, y=None):
27        """
28         Receive two vector x, y and prepare the slit calculator for
29         computation.
30       
31        :param x: array
32        :param y: array
33        """
34        self.x = x
35        self.y = y
36       
37    def calculate_slit_length(self):
38        """
39        Calculate slit length.
40       
41        :return: the slit length calculated value.
42        """
43        # None data do nothing
44        if self.y == None or self.x == None:
45            return
46        # set local variable
47        y = self.y
48        x = self.x
49
50        # find max y
51        max_y = y.max()
52       
53        # initial values
54        y_sum = 0.0
55        y_max = 0.0
56        ind = 0.0
57       
58        # sum 10 or more y values until getting max_y,
59        while (True):
60            if ind >= 10 and y_max == max_y:
61                break
62            y_sum = y_sum + y[ind]
63            if y[ind] > y_max: y_max = y[ind]
64            ind += 1
65     
66        # find the average value/2 of the top values 
67        y_half = y_sum/(2.0*ind)
68       
69        # defaults
70        y_half_d = 0.0
71        ind = 0.0
72        # find indices where it crosses y = y_half.
73        while (True):
74            ind += 1                # no need to check when ind == 0
75            y_half_d = y[ind]       # y value and ind just after passed the spot of the half height
76            if y[ind] < y_half: break
77   
78        y_half_u = y[ind-1]         # y value and ind just before passed the spot of the half height
79       
80        # get corresponding x values
81        x_half_d = x[ind]
82        x_half_u = x[ind-1] 
83       
84        # calculate x at y = y_half using linear interpolation
85        if y_half_u == y_half_d:
86            x_half = (x_half_d + x_half_u)/2.0
87        else:
88            x_half = (x_half_u * (y_half - y_half_d) + x_half_d*(y_half_u-y_half))/(y_half_u - y_half_d)
89       
90        # multiply by 2 due to the beam profile is for half beam
91        slit_length = 2.0 * x_half
92       
93        # set slit_length
94        self.slit_length = slit_length
95        return self.slit_length
96 
97    def get_slit_length_unit(self): 
98        """
99        :return: the slit length unit.
100        """
101        return self.slit_length_unit
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