Matplotlib 3.0 Cookbook
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Reading from external files and plotting

By default, Matplotlib accepts input data as a Python list, NumPy array, or pandas DataFrame. So all external data needs to be read and converted to one of these formats before feeding it to Matplotlib for plotting the graph. From a performance perspective, NumPy format is more efficient, but for default labels, pandas format is convenient. 

If the data is a .txt file, you can use NumPy function to read the data and put it in NumPy arrays. If the data is in .csv or .xlsx formats, you can use pandas to read the data. Here we will demonstrate how to read .txt, .csv, and .xlsx formats and then plot the graph.