60 lines
1.3 KiB
Python
60 lines
1.3 KiB
Python
import gemmi
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import numpy as np
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import matplotlib.pyplot as plt
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# -----------------------------
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# User input
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# -----------------------------
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mtz_file = "../data/Fext_tests_refine_5.mtz"
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F_label = "F-model"
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PHI_label = "PHIF-model"
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n_max = 30000
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# -----------------------------
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# Load MTZ
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# -----------------------------
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mtz = gemmi.read_mtz_file(mtz_file)
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F = np.array(mtz.column_with_label(F_label))[:n_max]
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PHI = np.array(mtz.column_with_label(PHI_label))[:n_max]
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# Convert to complex structure factors
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C = F * np.exp(1j * np.deg2rad(PHI))
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# -----------------------------
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# Head-to-tail vector plot
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# -----------------------------
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plt.figure(figsize=(7, 7))
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x_start, y_start = 0.0, 0.0 # first vector starts at origin
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for z in C:
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dx, dy = z.real, z.imag
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# draw arrow FROM (x_start, y_start) TO (x_start+dx, y_start+dy)
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plt.arrow(
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x_start, y_start,
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dx, dy,
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length_includes_head=True,
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head_width=0.03 * abs(z),
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alpha=0.6
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)
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# update start point for next vector
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x_start += dx
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y_start += dy
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# Mark start and end explicitly
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plt.scatter(0, 0, c="black", s=40, label="Start")
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plt.scatter(x_start, y_start, c="red", s=60, label="End")
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plt.xlabel("Re(F)")
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plt.ylabel("Im(F)")
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plt.title("Head-to-tail Argand plot of structure factors")
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plt.axis("equal")
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plt.grid(True)
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plt.legend()
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plt.show()
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