## Time Units

When you want to do computations like speed, or plot functions of time, you need to pick the time units.  You have two considerations:

1. What makes sense in the context of your data.  Do you have any feel for meters per second, or would km/hr be more intituitive, both for you and your audience?  (Since this is a science course, any inclination to use miles or inches must be resisted.)
2. What you have to do about the circularity of time.  For instance, if you have time that goes past midnight, you probably have to go with days.  If you then go over more than one month, you will have to use years (or Julian days).

You will usually have to proceed in two steps:

1. Break the time into discrete units (seconds, minutes, hours, days, months, years)
2. Recombine in one unit of time, say decimal hours.  While you will probably name your variable this way (it will be a floating point number) to distinguish it from the integer hours, when you refer to it in graph axis titles you will just say hours.  Because of the 60's and 24's and 365/6's in our time system, this involves some thinking.

last revised 1/12/2016