function out = pop_extract(data,regionid)
% out = pop_extract(data,regionid)
% Purpose: Extracts data for a single region from a 
%     multiregional population vector
% Input:
%     data = either a population or immigrant vector
%     regionid = a number from 1-9 representing the region
% Output:
%     A [36x1] population vector, with females 0-85+ 
%         and then males 0-85+;
% REGION IDS:
% 1 = Tahoe
% 2 = LA
% 3 = San Diego
% 4 = Fresno
% 5 = SF
% 6 = Sacramento
% 7 = Shasta
% 8 = Oregon
% 9 = Rest of US
i = regionid;
out = data(i:9:315+i);