DOC: Update some plotting code to current Matplotlib idioms

- 3D Axes are created via add_subplot(projection='3d')
- There is now a `stairs()` function that's specifically designed for
  showing histogram curves
- Labels should be passed as keyword arguments to the plot functions
  instead of to `legend()`, which reduces the risk of mixing them up.
- ensure equal axis scaling in the meshgrid example

1 files changed, 4 insertions, 2 deletions

diff --git a/doc/source/reference/routines.polynomials.classes.rst b/doc/source/reference/routines.polynomials.classes.rst
index 10331e9c1..5f575bed1 100644
--- a/doc/source/reference/routines.polynomials.classes.rst
+++ b/doc/source/reference/routines.polynomials.classes.rst
@@ -290,7 +290,8 @@ polynomials up to degree 5 are plotted below.
     >>> import matplotlib.pyplot as plt
     >>> from numpy.polynomial import Chebyshev as T
     >>> x = np.linspace(-1, 1, 100)
-    >>> for i in range(6): ax = plt.plot(x, T.basis(i)(x), lw=2, label="$T_%d$"%i)
+    >>> for i in range(6):
+    ...     ax = plt.plot(x, T.basis(i)(x), lw=2, label=f"$T_{i}$")
     ...
     >>> plt.legend(loc="upper left")
     <matplotlib.legend.Legend object at 0x3b3ee10>
@@ -304,7 +305,8 @@ The same plots over the range -2 <= `x` <= 2 look very different:
     >>> import matplotlib.pyplot as plt
     >>> from numpy.polynomial import Chebyshev as T
     >>> x = np.linspace(-2, 2, 100)
-    >>> for i in range(6): ax = plt.plot(x, T.basis(i)(x), lw=2, label="$T_%d$"%i)
+    >>> for i in range(6):
+    ...     ax = plt.plot(x, T.basis(i)(x), lw=2, label=f"$T_{i}$")
     ...
     >>> plt.legend(loc="lower right")
     <matplotlib.legend.Legend object at 0x3b3ee10>