Id of cities
Number of column before the census columns
Read the content of the file
Read the data part of the csv file
The dates of the census
Read the header of the csv file
Cities with hydrocarbons
Populations of the cities at the first date
Latitudes of the cities in decimal degrees
Longitudes of the cities in decimal degrees
Names of the cities
A vector of boolean, true in case a city is a national capital
Number of cities taken into account
The number of columns of census data
Column of population at a given date
Column of population at a given date
date of observation
an option containing the population if provided, none otherwise
Read the position of the cities
A vector of boolean, true in case a city is a regional capital
Regions of the cities
The cities with known populations for all dates
States cities belong to