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#!/opt/local/bin/python2.7 |
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'''An example script that generates a picture of the field lines for an electric field gradient.''' |
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import math |
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import VectorFieldPlot as vfp |
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# create a document. we specify the file name and image size here |
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doc = vfp.FieldplotDocument( 'Gradient', width=800,height=600,unit=100) |
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|
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# create a field opbject |
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field = vfp.Field() |
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# note, parameters are should be [ r_x, r_y, phi, q], where r is the position vector, phi is the angle of the quadrupole in radians, and q is the charge magnitude |
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field.add_element('gradient' , [ [ 1.0, 1.0, 0.0, 0.0, 1.0 ] ]) |
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# start drawing the field lines |
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#bottom up |
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N = 18 |
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for i in range(N): |
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x = -4 + 8 * float(i) / float(N) |
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y = -3 |
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# generate the line |
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# this takes the initial position, the x and y components of the initial direction, and whether or not should go forward |
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# or backward. |
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line = vfp.FieldLine( field, [x, y], start_v=[0, 1],directions='forward' ) |
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# draw the lin on the document |
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doc.draw_line(line,arrows_style={'min_arrows':1,'scale':0.4,'max_arrows':3}) |
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|
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#top down |
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for i in range(N): |
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x = -4 + 8 * float(i) / float(N) |
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y = 3 |
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# generate the line |
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# this takes the initial position, the x and y components of the initial direction, and whether or not should go forward |
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# or backward. |
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line = vfp.FieldLine( field, [x, y], start_v=[0, -1],directions='forward' ) |
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# draw the lin on the document |
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doc.draw_line(line,arrows_style={'min_arrows':1,'scale':0.4,'max_arrows':3}) |
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|
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#right left |
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for i in range(N): |
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x = 4 |
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y = -3 + 6 * float(i) / float(N) |
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# generate the line |
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# this takes the initial position, the x and y components of the initial direction, and whether or not should go forward |
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# or backward. |
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line = vfp.FieldLine( field, [x, y], start_v=[-1, 0],directions='forward' ) |
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# draw the lin on the document |
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doc.draw_line(line,arrows_style={'min_arrows':1,'scale':0.4,'max_arrows':3}) |
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|
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#left right |
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for i in range(N): |
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x = -4 |
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y = -3 + 6 * float(i) / float(N) |
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# generate the line |
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# this takes the initial position, the x and y components of the initial direction, and whether or not should go forward |
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# or backward. |
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line = vfp.FieldLine( field, [x, y], start_v=[1, 0],directions='forward' ) |
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# draw the lin on the document |
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doc.draw_line(line,arrows_style={'min_arrows':1,'scale':0.4,'max_arrows':3}) |
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doc.write() |
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