How can I produce student-style graphs using matplotlib?

Question

I am experimenting with matplotlib at the moment. Some time ago I used Excel VBA code to produce images such as the one attached.

You will notice it is not presented in a scientific/research style but rather as if produced by a school-student on graph paper - with three different grid-line styles.

Is there a fairly straightforward way to achieve this sort of thing with matplotlib?

Answer 1

Yes, you can use spines for this.

import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator, FormatStrFormatter
import numpy as np

fig = plt.figure(1)
ax = fig.add_subplot(111)

# set up axis
ax.spines['left'].set_position('zero')
ax.spines['right'].set_color('none')
ax.spines['bottom'].set_position('zero')
ax.spines['top'].set_color('none')
ax.xaxis.set_ticks_position('bottom')
ax.yaxis.set_ticks_position('left')

# draw curve
x = np.arange(-2.5,2.5,0.01)
line, = ax.plot(x, x**2)

#set bounds
ax.set_ybound(-1,7)

# create grid
#ax.xaxis.set_major_locator(MultipleLocator(1))
#ax.xaxis.set_minor_locator(MultipleLocator(0.2))
#ax.yaxis.set_major_locator(MultipleLocator(1))
#ax.yaxis.set_minor_locator(MultipleLocator(0.2))
#ax.xaxis.grid(True,'minor')
#ax.yaxis.grid(True,'minor')
#ax.xaxis.grid(True,'major',linewidth=2)
#ax.yaxis.grid(True,'major',linewidth=2)

#adjust grid on the 2s
#for idx,loc in enumerate(ax.xaxis.get_majorticklocs()):
    #if loc !=0 and loc % 2 == 0: ax.get_xgridlines()[idx].set_c('r')
#for idx,loc in enumerate(ax.yaxis.get_majorticklocs()):
    #if loc !=0 and loc % 2 == 0: ax.get_ygridlines()[idx].set_c('r')

## THIS IS THE EDIT
ax.xaxis.set_minor_locator(MultipleLocator(0.2))
ax.yaxis.set_minor_locator(MultipleLocator(0.2))
ax.xaxis.grid(True,'minor',linewidth=2)
ax.yaxis.grid(True,'minor',linewidth=2)

minor_grid_lines = [tick.gridline for tick in ax.xaxis.get_minor_ticks()]
for idx,loc in enumerate(ax.xaxis.get_minorticklocs()):
    if loc % 2.0 == 0: minor_grid_lines[idx].set_c('r' )
    elif loc % 1.0 == 0: minor_grid_lines[idx].set_c('g' )
    else: minor_grid_lines[idx].set_c( 'b' )

plt.show()

Answer 2

Just another thought - I have also tried to do it all with the minor gridlines (apart from anything else it will help my understanding), but it's not enumerating properly, no doubt due to the get_minorticklocs and ax.get_xgridlines. Sorry, and thanks in advance...

Geddes

import matplotlib.pyplot as plt 
from matplotlib.ticker import MultipleLocator, FormatStrFormatter 
import numpy as np 

fig = plt.figure(1) 
ax = fig.add_subplot(111) 

# set up axis 
ax.spines['left'].set_position('zero') 
ax.spines['right'].set_color('none') 
ax.spines['bottom'].set_position('zero') 
ax.spines['top'].set_color('none') 
ax.xaxis.set_ticks_position('bottom') 
ax.yaxis.set_ticks_position('left') 

# draw curve 
x = np.arange(-2.5,2.5,0.01) 
line, = ax.plot(x, x**2) 

#set bounds 
ax.set_ybound(-1,7) 

# create grid 
ax.xaxis.set_minor_locator(MultipleLocator(0.2)) 
ax.yaxis.set_minor_locator(MultipleLocator(0.2)) 
ax.xaxis.grid(True,'minor',linewidth=2) 
ax.yaxis.grid(True,'minor',linewidth=2) 

#adjust grid on the 2s 
for idx,loc in enumerate(ax.xaxis.get_minorticklocs()):
    if loc % 2 == 0: ax.get_xgridlines()[idx].set_color('r')
    if loc % 1 == 0: ax.get_xgridlines()[idx].set_color('g')
    if loc % 0.2 == 0: ax.get_xgridlines()[idx].set_color('b')

for idx,loc in enumerate(ax.yaxis.get_majorticklocs()): 
    if loc % 2 == 0: ax.get_ygridlines()[idx].set_c('b') 

plt.savefig('spines3.png',dpi=300)