Lily edits (#378)

* Implemented edits for pages 31 and 32

* Implemented grammar fixes for pages 33-34

* Implemented grammatical fixes for pages 31-40

* Updated Matplotlib file to fix pre-commit

core/cartopy.md

@@ -1,7 +1,6 @@
 # Cartopy
 
-This section contains tutorials on plotting maps with [Cartopy](https://scitools.org.uk/cartopy/docs/latest/).
-It will be cross-referenced with tutorials on [Xarray](xarray) and [Matplotlib](matplotlib).
+This section contains tutorials on plotting maps with [Cartopy](https://scitools.org.uk/cartopy/docs/latest/); it is cross-referenced with tutorials on [Xarray](xarray) and [Matplotlib](matplotlib).
 
 ---
 
@@ -16,6 +15,6 @@ From the [Cartopy website](https://scitools.org.uk/cartopy/docs/latest):
 > Key features of Cartopy are its object-oriented [projection definitions](https://scitools.org.uk/cartopy/docs/latest/reference/crs.html#list-of-projections),
 > and its ability to transform points, lines, vectors, polygons and images between those projections.
 
-You should have a basic familiarity with [Matplotlib](matplotlib) prior to working through the Cartopy notebooks presented here.
+Before working through the Cartopy notebooks in this section of Pythia Foundations, you should first have a basic knowledge of [Matplotlib](matplotlib).
 
-Cartopy's cartographic features library includes shapefiles directly served by [Natural Earth](https://www.naturalearthdata.com/).
+In addition, please note that the geographic-features library used by Cartopy makes use of shapefiles directly served by [Natural Earth](https://www.naturalearthdata.com/).

core/datetime.md

@@ -4,11 +4,11 @@
 This content is under construction!
 ```
 
-This section contains tutorials on dealing with times and calendars in scientific Python, beginning with use of the [datetime](https://docs.python.org/3/library/datetime.html) standard library.
+This section contains tutorials on dealing with times and calendars in scientific Python. The first and most basic of these tutorials covers the standard Python library known as [datetime](https://docs.python.org/3/library/datetime.html).
 
-When this chapter is fully built out, it will include a comprehensive guide to different time libraries and when/where to use them, including
+When this chapter is fully built out, it will include a comprehensive guide to different time libraries, where to use them, and when they might be useful. This set of time libraries includes these libraries, among others:
 
-- [Numpy `datetime64`](https://numpy.org/doc/stable/reference/arrays.datetime.html) for efficient vectorized datetime operations
-- [cftime library](https://unidata.github.io/cftime/) for dealing with non-standard calendars
+- [Numpy `datetime64`](https://numpy.org/doc/stable/reference/arrays.datetime.html) (for efficient vectorized date and time operations)
+- [cftime library](https://unidata.github.io/cftime/) (for dealing with dates and times in non-standard calendars)
 
-These will be cross-referenced with tutorials on dealing with timeseries data in [Pandas](pandas) and [Xarray](xarray).
+These tutorials will be cross-referenced with other tutorials on time-related topics, such as dealing with timeseries data in [Pandas](pandas) and [Xarray](xarray).

core/matplotlib.md

@@ -2,23 +2,23 @@
 
 # Matplotlib
 
-[Matplotlib](https://matplotlib.org) is the go-to library for plotting within python, with numerous packages and libraries using Matplotlib as a base to build off of. If you were to learn a single plotting tool to keep in your toolbox, this is the package.
+[Matplotlib](https://matplotlib.org) is the go-to library for plotting within Python. Numerous packages and libraries build off of Matplotlib, making it the de facto standard Python plotting package. If you were to learn a single plotting tool to keep in your toolbox, this is it.
 
 ## Why Matplotlib?
 
-Matplotlib is a plotting library for Python and is often the first plotting package Python-learners encounter. You may be wondering, "Why learn Matplotlib? Why not [Seaborn](https://seaborn.pydata.org) or another plotting library first?"
+Matplotlib is a plotting library for Python and is often the first plotting package Python learners encounter. You may be wondering, "Why learn Matplotlib? Why not [Seaborn](https://seaborn.pydata.org) or another plotting library first?"
 
-The simple answer is because of Matplotlib's popularity. Matplotlib is one of the most popular Python packages. Because of its history as Python's "go-to" plotting package, most other open source plotting libraries (including Seaborn) are built on top of Matplotlib and thus these more specialized plotting packages still inherit some of Matplotlib's capabilities, syntax, and limitations. You will find it useful to be familiar with Matplotlib when learning other plotting libraries.
+The simple answer to the much-asked question of "why Matplotlib?" is that it is extremely popular; in fact, Matplotlib is one of the most popular Python packages. Because of its history as Python's "go-to" plotting package, most other open source plotting libraries, including Seaborn, are built on top of Matplotlib; thus, these more specialized plotting packages inherit some of Matplotlib's capabilities, syntax, and limitations. Thus, you will find it useful to be familiar with Matplotlib when learning other plotting libraries.
 
-Matplotlib supports a variety of output formats, chart types, and interactive options, and runs well on most operating systems and graphic backends. The key feature to Matplotlib is its extensibility and the [extensive documentation](https://matplotlib.org) available to the community. These reasons are part of "Why Matplotlib" is so popular, and the first plotting language we will introduce you to in this book.
+Matplotlib supports a variety of output formats, chart types, and interactive options, and runs well on most operating systems and graphic backends. The key features of Matplotlib are its extensibility and the [extensive documentation](https://matplotlib.org) available to the community. All of these things contribute to Matplotlib's popularity, which is the answer to the question of "Why Matplotlib", and the reason Matplotlib is the first plotting package we will introduce you to in this book.
 
 ## In this section
 
-This section contains tutorials on basic plotting with [Matplotlib](https://matplotlib.org).
+In this section of Pythia Foundations, you will find tutorials on basic plotting with [Matplotlib](https://matplotlib.org).
 
-From the [Matplotlib documentation](https://matplotlib.org) "Matplotlib is a comprehensive library for creating static, animated, and interactive visualizations in Python."
+From the [Matplotlib documentation](https://matplotlib.org), "Matplotlib is a comprehensive library for creating static, animated, and interactive visualizations in Python."
 
-Currently, we provide a basic introduction to Matplotlib, as well as:
+Currently, Pythia Foundations provides a basic introduction to Matplotlib, as well as:
 
 - Histograms
 - Piecharts