Show Axes updating in "Embedding in Tk" example (matplotlib#20218)

* Update plot in tk-embedding example

* Flake 8 fix

* Change from button to slider

* Fix linting.

* Update data via set_data().

* Labels to physical units.

* Update examples/user_interfaces/embedding_in_tk_sgskip.py

Co-authored-by: Elliott Sales de Andrade <[email protected]>

* Update examples/user_interfaces/embedding_in_tk_sgskip.py

Co-authored-by: Elliott Sales de Andrade <[email protected]>

Co-authored-by: Elliott Sales de Andrade <[email protected]>

Author: kopytjuk

examples/user_interfaces/embedding_in_tk_sgskip.py

@@ -21,7 +21,10 @@
 
 fig = Figure(figsize=(5, 4), dpi=100)
 t = np.arange(0, 3, .01)
-fig.add_subplot().plot(t, 2 * np.sin(2 * np.pi * t))
+ax = fig.add_subplot()
+line, = ax.plot(t, 2 * np.sin(2 * np.pi * t))
+ax.set_xlabel("time [s]")
+ax.set_ylabel("f(t)")
 
 canvas = FigureCanvasTkAgg(fig, master=root)  # A tk.DrawingArea.
 canvas.draw()
@@ -30,18 +33,34 @@
 toolbar = NavigationToolbar2Tk(canvas, root, pack_toolbar=False)
 toolbar.update()
 
-
 canvas.mpl_connect(
     "key_press_event", lambda event: print(f"you pressed {event.key}"))
 canvas.mpl_connect("key_press_event", key_press_handler)
 
-button = tkinter.Button(master=root, text="Quit", command=root.quit)
+button_quit = tkinter.Button(master=root, text="Quit", command=root.quit)
+
+
+def update_frequency(new_val):
+    # retrieve frequency
+    f = float(new_val)
+
+    # update data
+    y = 2 * np.sin(2 * np.pi * f * t)
+    line.set_data(t, y)
+
+    # required to update canvas and attached toolbar!
+    canvas.draw()
+
+
+slider_update = tkinter.Scale(root, from_=1, to=5, orient=tkinter.HORIZONTAL,
+                              command=update_frequency, label="Frequency [Hz]")
 
 # Packing order is important. Widgets are processed sequentially and if there
 # is no space left, because the window is too small, they are not displayed.
 # The canvas is rather flexible in its size, so we pack it last which makes
 # sure the UI controls are displayed as long as possible.
-button.pack(side=tkinter.BOTTOM)
+button_quit.pack(side=tkinter.BOTTOM)
+slider_update.pack(side=tkinter.BOTTOM)
 toolbar.pack(side=tkinter.BOTTOM, fill=tkinter.X)
 canvas.get_tk_widget().pack(side=tkinter.TOP, fill=tkinter.BOTH, expand=1)