explain_data

Dataframe explanations:
  
>ld.total: all CDC case and PRISM climate data per county 

>ld.pop: same as ld.total but with population added; seperate dataframe necessary because population data only goes until 2014

>countyTick: Tick presence data per county

>ld.tick: all climate, cdc, and tick current, past, and future presence per county

>ld.tick.county: same as ld.tick but with County corrections to merge with county_map database

>ld.av.edit: average case count for counties

>case.0: average case count for counties with 0 tick presence

>case.1: case.0 counties with >1 av.case

>case.2: case.0 counties with >2 av.case

>jobs_map: all previous county data plus unemployment rate for counties where ticks are present (Presence_current=1)

>ld.pres.total: all previous county data plus deer data for counties where ticks are present 

>ld.pop.edit: all previous county data plus population for counties where ticks are present

>u: State level summaries of average cases, average unemployment rate, and total cases 2007-2015

>u250up: subset of u of states with more than 250 cases

>z: same as u plus total population and incidence measure (100,000*(total cases/total population))

>z big: subset of z of states with incidence > 0.03