Encode/Decode/Nintendo 64

Why Care Block:
Base64 encoding is extremely common when using API services, such as the Fitbit API, but that’s about all I know.  It’s necessary to get the job done and isn’t readily available in Stata.

Happy New Year!  We're starting 2016 with a bang, including this three part series on acquiring Fitbit data through Fitbit’s API services.  2015 was a great year and marked the start of this website, and I can guarantee that there will be much more content to come.  See the new "Why Care Block"?  It’s inspired by a Holiday conversation with family and gives a brief synopsis of why we’re even doing this in the first place.  With that, let's talk about the topic of the day: Base64 encoding.

Base64 encoding exists for some privacy purpose.  That's about all I want to say about Base64 encoding.  Let's just look at an example, they’re a lot cooler.

Say for instance we have the phrase: “This is kinda boring…”

By converting every character to ASCII bytes (and by potentially adding padding), converting each byte to base 2, taking the 8-bit representation of the binary character and convert it to a six bits, converting that back to base 10, and using those numbers (they fall between 0 and 63) to look up the corresponding character of the alphabet plus two other characters, we finally arrive at the following encoded string:

"VGhpcyBpcyBraW5kYSBib3JpbmcuLi4="

While they mean the same thing, I think the first phrase was a little more accurate.  We can encode this second phrase a second time and it gives us:

"VkdocGN5QnBjeUJyYVc1a1lTQmliM0pwYm1jdUxpND0="

Now you can easily send encoded messages to your friend (not plural – I can't imagine that many people would tolerate this type of behavior).  I’ve put together a Stata package containing these routines; however, no help file is available upon the first release.  Here is a brief overview of the new commands, encode64 and decode64 at work.

We first called encode64 on the string "client_id:123456789" to encode this value in Base64.  The result shows under the command, but is also callable through the macro r(base64).  We create a local macro that contains this encoded value ("Y2xpZW50X2lkOjEyMzQ1Njc4OQ==") and decode this message to get back to our original string.  It's a lot less fun than my old Nintendo 64, but trust me, the results will be extremely rewarding!  Feel free to download the ado file below.

encode64.ado
File Size:	2 kb
File Type:	ado

Download File

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Part 2: Getting Heart Rate Data with Stata, Fitbit's API, and cURL