# source:sasview/src/sas/sascalc/calculator/slit_length_calculator.py@b699768

Last change on this file since b699768 was b699768, checked in by Piotr Rozyczko <piotr.rozyczko@…>, 4 years ago

Initial commit of the refactored SasCalc? module.

• Property mode set to `100644`
File size: 2.8 KB
Line
1"""
2This module is a small tool to allow user to quickly
3determine the slit length value of data.
4"""
5
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:
64                y_max = y[ind]
65            ind += 1
66
67        # find the average value/2 of the top values
68        y_half = y_sum/(2.0*ind)
69
70        # defaults
71        y_half_d = 0.0
72        ind = 0.0
73        # find indices where it crosses y = y_half.
74        while True:
75            # no need to check when ind == 0
76            ind += 1
77            # y value and ind just after passed the spot of the half height
78            y_half_d = y[ind]
79            if y[ind] < y_half:
80                break
81
82        # y value and ind just before passed the spot of the half height
83        y_half_u = y[ind-1]
84
85        # get corresponding x values
86        x_half_d = x[ind]
87        x_half_u = x[ind-1]
88
89        # calculate x at y = y_half using linear interpolation
90        if y_half_u == y_half_d:
91            x_half = (x_half_d + x_half_u)/2.0
92        else:
93            x_half = (x_half_u * (y_half - y_half_d)  \
94                       + x_half_d * (y_half_u - y_half)) \
95                        / (y_half_u - y_half_d)
96
97        # Our slit length is half width, so just give half beam value
98        slit_length = x_half
99
100        # set slit_length
101        self.slit_length = slit_length
102        return self.slit_length
103
104    def get_slit_length_unit(self):
105        """
106        :return: the slit length unit.
107        """
108        return self.slit_length_unit
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