*Biostat 212 2018: Lecture 3 - Data cleaning
* Dates activity


clear

* STEP 1: Input dates 

gen str8 baseline = ""
input
"08/03/17"
"03/22/16"
"06/18/17"
"10/12/16"
"05/30/17"
end
 


* STEP 2: create a new variable called "visit0" from  "baseline" 
gen visit0 = date(baseline, "MDY", 2018)

 

* STEP 3: format "visit0" so you can understand it 
format visit0 %td



*STEP 4: simple addition/subtraction

gen visit1 = visit0 + 10
format visit1 %td

gen delta = visit1 - visit0



*STEP 5: extracting components of dates
gen year = year(visit0)


gen dow = dow(visit0)  // dow = day of week

label define dowlabel 0 "Sunday" 1 "Monday" 2 "Tuesday" 3 "Wednesday" 4 "Thursday" 5 "Friday" 6 "Saturday"
label values dow dowlabel