add more comments. add a reference section

chrissshe · chrissshe · commit 51784a9bb3cb · 2020-02-17T21:48:12.000-08:00
diff --git a/examples/widgets/textbox.py b/examples/widgets/textbox.py
@@ -5,9 +5,13 @@
 
 Allowing text input with the Textbox widget.
 
-You can use the Textbox widget to let users provide any text that needs to be
-displayed, including formulas. You can use a submit button to create plots
-with the given input.
+You can use the Textbox widget to let users interactively provide any text 
+that needs to be displayed, including formulas. You can use a submit button to 
+create plots with the given input.
+
+Note to not get confused with 
+:doc:`/tutorials/text/annotations` and 
+:doc:`/gallery/recipes/placing_text_boxes`, both of which are static elements.
 """
 
 import numpy as np
@@ -22,7 +26,9 @@
 
 
 def submit(text):
-    ydata = eval(text)
+    # user can enter a new math expression that uses "t" as its independent 
+    # variable. The plot refreshes on entering. Example: try "t ** 3"
+    ydata = eval(text)  
     l.set_ydata(ydata)
     ax.set_ylim(np.min(ydata), np.max(ydata))
     plt.draw()
@@ -32,3 +38,15 @@ def submit(text):
 text_box.on_submit(submit)
 
 plt.show()
+
+#############################################################################
+#
+# ------------
+#
+# References
+# """"""""""
+#
+# The use of the following functions, methods, classes and modules is shown
+# in this example:
+
+from matplotlib.widgets import TextBox
