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I am in an interesting situation. I have the diagram's image with axis

IMG

So when I try to plot this diagram wiht the next code:

plt.figure("Ti Zr")
ax = plt.subplot(111)
im = plt.imshow(np.flipud(plt.imread('Ti_ZrB.png')), 
    origin='lower', 
    extent=[0, 800, 1000, 32700])
plt.xticks([10,15, 43, 95, 215,542,800])
plt.yticks([1000, 1860, 2670, 8600, 16600,32700])

plt.axis('normal')
plt.show()

Before uploading the image I have just only cut out the axis numbers on Corel. Finaly I have got this

IMG

As you can see the axis has been displaced and they are not in their own place. Usually i use this way to plotting diagrams and before I haven't any problems whit it. But now I haven't any idea. Thank you in advance. I would be so grateful for some help

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3  
Your original has a non-linear axes, it might be logarithmic. To match the ticks, you need to figure out what the function is. – tcaswell Feb 3 at 17:39
So how I can understood the one way only it is find the function? – Protoss Reed Feb 4 at 15:16
plot the pixel positions of the ticks vs the number on them and try to guess the from. – tcaswell Feb 4 at 15:50

1 Answer

up vote 2 down vote accepted

You can use mouse-click events in matplotlib to easily determine the coordinates of the ticks instead of guessing it. 

import numpy as np
import matplotlib.pyplot as plt

def tell_click_coordinates(event):
    print "X: %.0f, Y: %.0f" % (event.xdata, event.ydata)

fig = plt.figure("Ti Zr")
fig.canvas.mpl_connect("button_press_event", tell_click_coordinates)

ax = plt.subplot(111)
im = plt.imshow(np.flipud(plt.imread('14675002_in.png')), 
    origin='lower', 
    extent=[0, 800, 1000, 32700])
plt.xticks([10,15, 43, 95, 215,542,800])
plt.yticks([1000, 1860, 2670, 8600, 16600,32700])

plt.axis('normal')
plt.show()

Clicking one tick after the other will give you:

X: 6, Y: 1576
X: 6, Y: 6902
X: 10, Y: 13037
X: 8, Y: 20415
X: 11, Y: 26383
X: 76, Y: 2177
X: 260, Y: 1846
X: 494, Y: 1846
X: 594, Y: 1680
X: 715, Y: 1928

Then, you can adjust your plot with these values:

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure("Ti Zr")

ax = plt.subplot(111)
im = plt.imshow(np.flipud(plt.imread('14675002_in.png')), 
    origin='lower', 
    extent=[0, 800, 1000, 32700])
plt.xticks([76,260,494,594,715,800],[10,15, 43, 95, 215,542,800])
plt.yticks([1576,6902, 13037, 20415, 26383, 32700],[1000, 1860, 2670, 8600, 16600,32700])

plt.axis('normal')
plt.show()

and you get

result

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Thank you very much! This is really useful, all what I need ) – Protoss Reed Feb 5 at 14:12

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