Page - 24 - in Programming for Computations – Python - A Gentle Introduction to Numerical Simulations with Python 3.6, Volume Second Edition

24 1 TheFirstFewSteps Fig. 1.2 Vertical position of the ball computed and plotted for every 0.1s Decoratinga Plot We have seen how the code linesplt.xlabel(’t (s)’)and plt.ylabel(’y (m)’) in ball_plot.pyput labelst (s) andy (m) on the t- andy-axis, respectively.Thereareotherways toenrichaplotaswell. One thing, is to add a legend so that the curve itself gets labeled. With ball_plot.py, we could get the legend v0*t - 0.5*g*t**2, for example, by coding plt.legend([’v0*t - 0.5*g*t**2’]) Whenthere ismore thana singlecurve,a legendisparticularly importantofcourse (seesectionbelowon“multiplecurves” fora plotexample). Another thing, is to add a grid. This is useful when you want a more detailed impressionof thecurveandmaybecoded in thisway, plt.grid(’on’) Aplotmayalsogeta title on top.To geta title likeThis is a great title, for example,we couldwrite plt.title(’This is a great title’) Sometimes, thedefault rangesappearingon theaxesarenotwhatyouwant themto be.Thismaythenbespecifiedbya code line like plt.axis([0, 1.2, -0.2, 1.5]) # x in [0, 1.2] and y in [-0.2, 1.5] All statements just explainedwill be demonstrated in the next section, when we showhowmultiplecurvesmaybeplotted together ina singleplot. Multiple Curves in the Same Plot Assume we want to plot f(t) = t2 and g(t) = et in the same plot for t on the interval [−2,2]. The following script (plot_multiple_curves.py)will accomplish this task: import numpy as np import matplotlib.pyplot as plt