python - Location of contour lines -
below code , plot:
import matplotlib import matplotlib.mlab mlab import matplotlib.cm cm import matplotlib.pyplot plt import numpy np %matplotlib inline delta = 0.00025 a=0 x = np.arange(0, 0.10, delta) y = np.arange(0, 0.1, delta) x, y = np.meshgrid(x, y) z = a*(x**2+y**2)+2*x*y manual_locations = [(0.1,0.1), (0.2,0.2), (0.3,0.3), (0.015, 0.015), (0.00255, 0.0025), (0.00005,0.00005)] line_widths = (1, 1, 1, 1, 1, 1) plt.figure() cs = plt.contour(x, y, z, 6, # add 6 contour lines linewidths=line_widths, # line widths colors = line_colours) # line colours plt.clabel(cs, inline=1, # add labels fontsize=10, # label font size manual=manual_locations) # label locations plt.title('indifference map') # title plt.show() 
it seems manual_locations nothing, python picks equally spaced contour lines automatically. while want investigate more details around 0. how can see more curves/contour lines converging (0,0)? in advance.
the easiest way explore parts of data in more details levels. sets z-values examine, , in question phrase (x,y) location inspect, it's bit backwards how contour works specify location points directly.
you inspect (0,0) region changing boundaries of plot appropriately.
below, use log values levels, linear values work equally well, far more common, , easier interpret. log values emphasis part of plot you're interested in.
import matplotlib import matplotlib.mlab mlab import matplotlib.cm cm import matplotlib.pyplot plt import numpy np #%matplotlib inline delta = 0.00025 a=0 x = np.arange(0, 0.10, delta) y = np.arange(0, 0.1, delta) x, y = np.meshgrid(x, y) z = a*(x**2+y**2)+2*x*y manual_locations = [(0.1,0.1), (0.2,0.2), (0.3,0.3), (0.015, 0.015), (0.00255, 0.0025), (0.00005,0.00005)] line_widths = (1, 1, 1, 1, 1, 1) plt.figure() cs = plt.contour(x, y, z, 6, # add 6 contour lines linewidths=line_widths, #levels=np.linspace(0, .003, 20)) levels=np.logspace(-5, -2, 20)) plt.clabel(cs, inline=1, # add labels fontsize=10, fmt="%.5f") plt.title('indifference map') # title plt.show() if need contour @ specific location, put (x,y) values location equation calculate z-value @ location, , use value 1 of values in levels argument.
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