1 | """ |
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2 | This module is a small tool to allow user to quickly |
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3 | determine the slit length value of data. |
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4 | """ |
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5 | |
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6 | |
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7 | class SlitlengthCalculator(object): |
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8 | """ |
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9 | compute slit length from SAXSess beam profile (1st col. Q , 2nd col. I , |
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10 | and 3rd col. dI.: don't need the 3rd) |
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11 | """ |
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12 | def __init__(self): |
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13 | |
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14 | # x data |
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15 | self.x = None |
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16 | # y data |
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17 | self.y = None |
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18 | # default slit length |
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19 | self.slit_length = 0.0 |
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20 | |
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21 | # The unit is unknown from SAXSess profile: |
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22 | # It seems 1/nm but it could be not fixed, |
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23 | # so users should be notified to determine the unit by themselves. |
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24 | self.slit_length_unit = "unknown" |
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25 | |
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26 | def set_data(self, x=None, y=None): |
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27 | """ |
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28 | Receive two vector x, y and prepare the slit calculator for |
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29 | computation. |
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30 | |
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31 | :param x: array |
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32 | :param y: array |
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33 | """ |
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34 | self.x = x |
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35 | self.y = y |
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36 | |
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37 | def calculate_slit_length(self): |
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38 | """ |
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39 | Calculate slit length. |
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40 | |
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41 | :return: the slit length calculated value. |
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42 | """ |
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43 | # None data do nothing |
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44 | if self.y is None or self.x is None: |
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45 | return |
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46 | # set local variable |
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47 | y = self.y |
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48 | x = self.x |
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49 | |
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50 | # find max y |
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51 | max_y = y.max() |
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52 | |
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53 | # initial values |
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54 | y_sum = 0.0 |
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55 | y_max = 0.0 |
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56 | ind = 0 |
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57 | |
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58 | # sum 10 or more y values until getting max_y, |
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59 | while True: |
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60 | if ind >= 10 and y_max == max_y: |
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61 | break |
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62 | y_sum = y_sum + y[ind] |
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63 | if y[ind] > y_max: |
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64 | y_max = y[ind] |
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65 | ind += 1 |
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66 | |
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67 | # find the average value/2 of the top values |
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68 | y_half = y_sum/(2.0*ind) |
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69 | |
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70 | # defaults |
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71 | y_half_d = 0.0 |
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72 | ind = 0 |
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73 | # find indices where it crosses y = y_half. |
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74 | while True: |
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75 | # no need to check when ind == 0 |
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76 | ind += 1 |
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77 | # y value and ind just after passed the spot of the half height |
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78 | y_half_d = y[ind] |
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79 | if y[ind] < y_half: |
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80 | break |
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81 | |
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82 | # y value and ind just before passed the spot of the half height |
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83 | y_half_u = y[ind - 1] |
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84 | |
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85 | # get corresponding x values |
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86 | x_half_d = x[ind] |
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87 | x_half_u = x[ind - 1] |
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88 | |
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89 | # calculate x at y = y_half using linear interpolation |
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90 | if y_half_u == y_half_d: |
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91 | x_half = (x_half_d + x_half_u)/2.0 |
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92 | else: |
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93 | x_half = ((x_half_u * (y_half - y_half_d) |
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94 | + x_half_d * (y_half_u - y_half)) |
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95 | / (y_half_u - y_half_d)) |
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96 | |
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97 | # Our slit length is half width, so just give half beam value |
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98 | slit_length = x_half |
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99 | |
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100 | # set slit_length |
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101 | self.slit_length = slit_length |
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102 | return self.slit_length |
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103 | |
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104 | def get_slit_length_unit(self): |
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105 | """ |
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106 | :return: the slit length unit. |
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107 | """ |
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108 | return self.slit_length_unit |
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