How to shift axis and redefine origin in Matplotlib graph?

Question

I am plotting a double-slit diffraction experiment graph using Matplotlib in Python. What I want is to shift the graph so that the central maximum is at 0. (Right now the maximum of voltage occurs at x=2.7 mm). How can I do that?

Double slit diffraction experiment plot

plt.style.use('ggplot')
x = df['Position']
y = df['Voltage']
plt.figure(figsize=(8,6))
plt.plot(x,y, marker='.', markersize=14, linewidth=3.5, color='#5f5f5f')
plt.ylim(0,4)
plt.xlabel('Position[mm]', fontsize=15)
plt.ylabel('Voltage[V]', fontsize=15)
plt.xticks(fontsize=13)
plt.yticks(fontsize=13)
plt.title('Position v.s. Voltage Plot for Two Slit Diffraction', fontsize=18)
plt.savefig('2slit')
plt.show()

Please see the link for the image of my plot.

JetsonDIPG
– JetsonDIPG

2020-03-25 04:19:16 +00:00
Commented Mar 25, 2020 at 4:19 — JetsonDIPG
– JetsonDIPG, Commented Mar 25, 2020 at 4:19

William Miller · Accepted Answer · 2020-03-25 04:53:22Z

3

You can find the index of the maximum on the fly with numpy.argmax and then subtract from the x array accordingly:

import numpy as np
#...
x = df['Position'].values
y = df['Voltage'].values
shift = x[np.argmax(y)]
plt.plot(x - shift,y, marker='.', markersize=14, linewidth=3.5, color='#5f5f5f')

Note that this will not work if there are two equal maxima.

answered Mar 25, 2020 at 4:53

William Miller

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