9.5 Long format data

• Longformat: Observations of same units are stacked on top of each other
  • Row = unit \(\times\) time = observations
  • Columns: unit id, time and variables that are spread out (rarely variables are also stacked)
  • Table 9.2 below is “real” longformat accepted by most stat software
• Use tidyr package (alternatives reshape package)
  • pivot_longer() to collect variables into one column, separate to generate two columns for variables and time (here separator is a “.”) and pivot_wider() to spread variables across columns keeping time column
  • To my knowledge pivot_longer(), pivot_wider() were introduced after neg. community feedback to replace gather() and spread()

Table 9.2: Long format

unit	time	trust	Victimization
Paul	2006	5	0
Paul	2007	5	1
Pedro	2006	6	1
Pedro	2007	6	0
Peter	2006	1	0
Peter	2007	1	1