Coverage for chebpy/core/plotting.py: 100%

1"""Plotting utilities for visualizing functions and their properties. 

2 

3This module provides functions for plotting functions, their coefficients, and 

4other visualizations useful for understanding function approximations. It uses 

5matplotlib for the actual plotting, but is designed to gracefully handle cases 

6where matplotlib is not available. 

7 

8The main functions are: 

9- plotfun: Plot a function over a specified interval 

10- plotfuncoeffs: Plot the coefficients of a function on a semilogy scale 

11 

12These functions are typically used by higher-level classes like Chebfun and 

13Chebtech to provide plotting capabilities. 

14""" 

15 

16import matplotlib.pyplot as plt 

17import numpy as np 

18 

19from .settings import _preferences as prefs 

20 

21 

22def plotfun(fun: callable, support: tuple, ax=None, n: int = None, **kwds) -> object: 

23 """Plot a function over a specified support interval. 

24 

25 This function plots a callable object over a specified interval using 

26 matplotlib. For complex-valued functions, it plots the real part against 

27 the imaginary part. 

28 

29 Args: 

30 fun (callable): The function to plot. Must be callable and have an 

31 'iscomplex' attribute. 

32 support (tuple): A tuple specifying the interval [a, b] over which to plot. 

33 ax (matplotlib.axes.Axes, optional): The axes on which to plot. If None, 

34 a new axes will be created. Defaults to None. 

35 n (int, optional): Number of points to use for plotting. If None, uses 

36 the value from preferences. Defaults to None. 

37 **kwds: Additional keyword arguments to pass to matplotlib's plot function. 

38 

39 Returns: 

40 matplotlib.axes.Axes: The axes on which the plot was created. 

41 """ 

42 ax = ax or plt.gca() 

43 n = n if n is not None else prefs.N_plot 

44 xx = np.linspace(*support, n) 

45 ff = fun(xx) 

46 if fun.iscomplex: 

47 ax.plot(np.real(ff), np.imag(ff), **kwds) 

48 ax.set_xlabel(kwds.pop("ylabel", "real")) 

49 ax.set_ylabel(kwds.pop("xlabel", "imag")) 

50 else: 

51 ax.plot(xx, ff, **kwds) 

52 return ax 

53 

54 

55def plotfuncoeffs(abscoeffs: np.ndarray, ax=None, **kwds) -> object: 

56 """Plot the absolute values of function coefficients on a semilogy scale. 

57 

58 This function creates a semilogy plot of the absolute values of function 

59 coefficients, which is useful for visualizing the decay of coefficients 

60 in a Chebyshev series. 

61 

62 Args: 

63 abscoeffs (numpy.ndarray): Array of absolute coefficient values to plot. 

64 ax (matplotlib.axes.Axes, optional): The axes on which to plot. If None, 

65 a new axes will be created. Defaults to None. 

66 **kwds: Additional keyword arguments to pass to matplotlib's semilogy function. 

67 

68 Returns: 

69 matplotlib.axes.Axes: The axes on which the plot was created. 

70 """ 

71 ax = ax or plt.gca() 

72 ax.set_ylabel(kwds.pop("xlabel", "coefficient magnitude")) 

73 ax.set_xlabel(kwds.pop("ylabel", "polynomial degree")) 

74 ax.semilogy(abscoeffs, **kwds) 

75 return ax