Added two folders and a markdown file

[eternalscholar]

Added the two folders data and images and also added the markdown file "Pandas time-stamp based filtering.md".

The markdown file illustrates reading csv files into Pandas data frame, assigning index columns before merging the dataframes, merging the dataframes, and efficiently filtering the dataframes. The merged dataframes are filtered based on columns that have values of the datatype "datetime".

[csbailey5t]

@eternalscholar and @mikenutt Is there another DSC to review this PR or should I?

[SRSchmittling]

Hi, Vishnu,

This looks great. Only one thing I might change. In a couple of places you use a variable name to print out the contents of the variable. This may not print out the data in all environments. I use Pycharm and I have to use a print statement to have the show the contents of a variable:

print(flightData)

I think the print() statement works in all environments, but I'm not sure...we could ask Scott B. If it does, I would just replace it in your instructions. Otherwise, you could add a caveat that the user may need to use the print() statement in some environments.

[csbailey5t]

@eternalscholar and @SRSchmittling Agreed on using explicit print statements, since we can't assume that people will run the code in notebook environments that would output the last line of a cell.

You might also look at adding alt tags to your images: https://github.github.com/gfm/#images.

[eternalscholar]

@csbailey5t @SRSchmittling Thank you both for reviewing this pull request and your comments. I have included the changes you suggested in my new commit. More specifically, I have included explicit "print" commands and included 'alt text' for images. You may now merge this pull request.