Pull in US Economic data from IMF database, pull out some columns and save as tab-delimited file. Updating to clarify the extraction algo and adding the write data algo.

munge_data.rb

require 'csv'

module MungeData

  # Open a tab-delimited data file converting it into a CSV structure, 
  # expecting the first row to be headers,
  # passing the table to map each row of the table,
  # converting each row to a hash and then selecting only
  # those items in the array that match the characteristics in the block
  def self.extract_years(censusdata, y_start, y_end)
    CSV.table(censusdata, col_sep: "\t").map do |r|
      r.to_hash.select do |k,v|
        true if (k =~ /^#{y_start}$/ .. k =~ /^#{y_end}/) || # a flip-flop that pulls keys from y_start to y_end
          k =~ /^subject_descriptor$/ || # the subject descriptor field
          k =~ /^weo_subject_code$/ # and the weo_subject_code
      end
    end
  end

  # Open a tab-delimited data file for writing,
  # Creating the header row from the keys of the first row of data.
  # Write all the rows from the data table using just the values.
  def self.write_tdv(outfile,data)
    CSV.open(outfile,'wb', col_sep: "\t") do |csv_file|
      csv_file << data.first.keys # write the header row
      data.each do |row|
        csv_file << row.values  # write the data row
      end
    end
  end

end


us_eco = MungeData.extract_years("weoreptc-us-all.xls","1980","2010")
MungeData.write_tdv("outfile.txt",us_eco)

outfile.txt

weo_subject_code	subject_descriptor	1980	1981	1982	1983	1984	1985	1986	1987	1988	1989	1990	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	2001	2002	2003	2004	2005	2006	2007	2008	2009	2010
NGDP_R	Gross domestic product, constant prices	5,833.975	5,982.075	5,865.925	6,130.925	6,571.525	6,843.400	7,080.500	7,307.050	7,607.400	7,879.175	8,027.025	8,008.325	8,280.025	8,516.175	8,863.125	9,085.975	9,425.850	9,845.925	10,274.750	10,770.625	11,216.425	11,337.475	11,543.100	11,836.425	12,246.925	12,622.950	12,958.475	13,206.375	13,161.925	12,757.950	13,062.975
NGDP_RPCH	Gross domestic product, constant prices	-0.275	2.539	-1.942	4.518	7.187	4.137	3.465	3.2	4.11	3.573	1.876	-0.233	3.393	2.852	4.074	2.514	3.741	4.457	4.355	4.826	4.139	1.079	1.814	2.541	3.468	3.07	2.658	1.913	-0.337	-3.069	2.391
NGDP	Gross domestic product, current prices	2,788.150	3,126.850	3,253.175	3,534.600	3,930.925	4,217.475	4,460.050	4,736.350	5,100.425	5,482.125	5,800.525	5,992.100	6,342.300	6,667.325	7,085.150	7,414.625	7,838.475	8,332.350	8,793.475	9,353.500	9,951.475	10,286.175	10,642.300	11,142.225	11,853.250	12,622.950	13,377.200	14,028.675	14,291.550	13,973.650	14,498.925
NGDPD	Gross domestic product, current prices	2,788.150	3,126.850	3,253.175	3,534.600	3,930.925	4,217.475	4,460.050	4,736.350	5,100.425	5,482.125	5,800.525	5,992.100	6,342.300	6,667.325	7,085.150	7,414.625	7,838.475	8,332.350	8,793.475	9,353.500	9,951.475	10,286.175	10,642.300	11,142.225	11,853.250	12,622.950	13,377.200	14,028.675	14,291.550	13,973.650	14,498.925
NGDP_D	Gross domestic product, deflator	47.792	52.27	55.459	57.652	59.818	61.628	62.991	64.819	67.046	69.577	72.262	74.823	76.598	78.29	79.94	81.605	83.159	84.627	85.583	86.843	88.722	90.727	92.196	94.135	96.786	100.0	103.231	106.227	108.583	109.529	110.993
NGDPRPC	Gross domestic product per capita, constant prices	25,630.111	26,018.562	25,270.235	26,172.963	27,809.240	28,703.671	29,429.409	30,101.040	31,054.732	31,862.611	32,102.011	31,604.511	32,245.955	32,736.084	33,658.555	34,099.067	34,964.859	36,089.179	37,224.343	38,577.439	39,732.863	39,750.499	40,077.564	40,712.308	41,743.018	42,628.552	43,349.542	43,743.745	43,193.789	41,506.310	42,175.090
NGDPPC	Gross domestic product per capita, current prices	12,249.040	13,599.987	14,014.584	15,089.233	16,634.805	17,689.601	18,537.764	19,511.165	20,820.823	22,169.176	23,197.700	23,647.566	24,699.626	25,629.125	26,906.527	27,826.601	29,076.547	30,541.333	31,857.839	33,501.684	35,251.927	36,064.520	36,949.993	38,324.553	40,401.197	42,628.552	44,750.288	46,467.466	46,900.905	45,461.429	46,811.195
NGDPDPC	Gross domestic product per capita, current prices	12,249.040	13,599.987	14,014.584	15,089.233	16,634.805	17,689.601	18,537.764	19,511.165	20,820.823	22,169.176	23,197.700	23,647.566	24,699.626	25,629.125	26,906.527	27,826.601	29,076.547	30,541.333	31,857.839	33,501.684	35,251.927	36,064.520	36,949.993	38,324.553	40,401.197	42,628.552	44,750.288	46,467.466	46,900.905	45,461.429	46,811.195
NGAP_NPGDP	Output gap in percent of potential GDP	-1.997	-1.117	-5.788	-4.386	-0.514	0.158	0.216	0.295	1.304	1.866	0.747	-2.16	-1.37	-1.156	0.067	-0.292	0.347	1.607	2.494	3.753	4.356	1.591	0.138	-0.078	0.546	1.348	1.787	1.409	-0.939	-5.559	-4.475

weoreptc-us-all.xls

WEO Country Code	ISO	WEO Subject Code	Country	Subject Descriptor	Subject Notes	Units	Scale	Country/Series-specific Notes	1980	1981	1982	1983	1984	1985	1986	1987	1988	1989	1990	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000	2001	2002	2003	2004	2005	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	Estimates Start After
111	USA	NGDP_R	United States	Gross domestic product, constant prices	Expressed in billions of national currency units; the base year is country-specific. Expenditure-based GDP is total final expenditures at purchasers? prices (including the f.o.b. value of exports of goods and services), less the f.o.b. value of imports of goods and services. [SNA 1993]	National currency	Billions	Source: Haver Analytics Latest actual data: 2011 GDP valuation: Real Gross Domestic Product determined by chained Fisher quantity growth rates. Start/end months of reporting year: January/December Base year: 2005 Chain-weighted: Yes, from 1980 Primary domestic currency: U.S. dollars Data last updated: 09/2012	5,833.975	5,982.075	5,865.925	6,130.925	6,571.525	6,843.400	7,080.500	7,307.050	7,607.400	7,879.175	8,027.025	8,008.325	8,280.025	8,516.175	8,863.125	9,085.975	9,425.850	9,845.925	10,274.750	10,770.625	11,216.425	11,337.475	11,543.100	11,836.425	12,246.925	12,622.950	12,958.475	13,206.375	13,161.925	12,757.950	13,062.975	13,299.100	13,587.652	13,875.222	14,282.756	14,762.231	15,265.684	15,773.899	2011
111	USA	NGDP_RPCH	United States	Gross domestic product, constant prices	Annual percentages of constant price GDP are year-on-year changes; the base year is country-specific . Expenditure-based GDP is total final expenditures at purchasers? prices (including the f.o.b. value of exports of goods and services), less the f.o.b. value of imports of goods and services. [SNA 1993]	Percent change		See notes for:  Gross domestic product, constant prices (National currency).	-0.275	2.539	-1.942	4.518	7.187	4.137	3.465	3.200	4.110	3.573	1.876	-0.233	3.393	2.852	4.074	2.514	3.741	4.457	4.355	4.826	4.139	1.079	1.814	2.541	3.468	3.070	2.658	1.913	-0.337	-3.069	2.391	1.808	2.170	2.116	2.937	3.357	3.410	3.329	2011
111	USA	NGDP	United States	Gross domestic product, current prices	Expressed in billions of national currency units . Expenditure-based GDP is total final expenditures at purchasers? prices (including the f.o.b. value of exports of goods and services), less the f.o.b. value of imports of goods and services. [SNA 1993]	National currency	Billions	Source: Haver Analytics Latest actual data: 2011 GDP valuation: Real Gross Domestic Product determined by chained Fisher quantity growth rates. Start/end months of reporting year: January/December Base year: 2005 Chain-weighted: Yes, from 1980 Primary domestic currency: U.S. dollars Data last updated: 09/2012	2,788.150	3,126.850	3,253.175	3,534.600	3,930.925	4,217.475	4,460.050	4,736.350	5,100.425	5,482.125	5,800.525	5,992.100	6,342.300	6,667.325	7,085.150	7,414.625	7,838.475	8,332.350	8,793.475	9,353.500	9,951.475	10,286.175	10,642.300	11,142.225	11,853.250	12,622.950	13,377.200	14,028.675	14,291.550	13,973.650	14,498.925	15,075.675	15,653.366	16,197.956	16,912.540	17,768.397	18,717.045	19,745.323	2011
111	USA	NGDPD	United States	Gross domestic product, current prices	Values are based upon GDP in national currency converted to U.S. dollars using market exchange rates (yearly average). Exchange rate projections are provided by country economists for the group of other emerging market and developing countries. Exchanges rates for advanced economies are established in the WEO assumptions for each WEO exercise. Expenditure-based GDP is total final expenditures at purchasers? prices (including the f.o.b. value of exports of goods and services), less the f.o.b. value of imports of goods and services. [SNA 1993]	U.S. dollars	Billions	See notes for:  Gross domestic product, current prices (National currency).	2,788.150	3,126.850	3,253.175	3,534.600	3,930.925	4,217.475	4,460.050	4,736.350	5,100.425	5,482.125	5,800.525	5,992.100	6,342.300	6,667.325	7,085.150	7,414.625	7,838.475	8,332.350	8,793.475	9,353.500	9,951.475	10,286.175	10,642.300	11,142.225	11,853.250	12,622.950	13,377.200	14,028.675	14,291.550	13,973.650	14,498.925	15,075.675	15,653.366	16,197.956	16,912.540	17,768.397	18,717.045	19,745.323	2011
111	USA	NGDP_D	United States	Gross domestic product, deflator	The GDP deflator is derived by dividing current price GDP by constant price GDP and is considered to be an alternate measure of inflation. Data are expressed in the base year of each country's national accounts.	Index		See notes for:  Gross domestic product, constant prices (National currency) Gross domestic product, current prices (National currency).	47.792	52.270	55.459	57.652	59.818	61.628	62.991	64.819	67.046	69.577	72.262	74.823	76.598	78.290	79.940	81.605	83.159	84.627	85.583	86.843	88.722	90.727	92.196	94.135	96.786	100.000	103.231	106.227	108.583	109.529	110.993	113.359	115.203	116.740	118.412	120.364	122.609	125.177	2011
111	USA	NGDPRPC	United States	Gross domestic product per capita, constant prices	GDP is expressed in constant national currency per person. Data are derived by dividing constant price GDP by total population.	National currency	Units	See notes for:  Gross domestic product, constant prices (National currency) Population (Persons).	25,630.111	26,018.562	25,270.235	26,172.963	27,809.240	28,703.671	29,429.409	30,101.040	31,054.732	31,862.611	32,102.011	31,604.511	32,245.955	32,736.084	33,658.555	34,099.067	34,964.859	36,089.179	37,224.343	38,577.439	39,732.863	39,750.499	40,077.564	40,712.308	41,743.018	42,628.552	43,349.542	43,743.745	43,193.789	41,506.310	42,175.090	42,632.722	43,229.954	43,735.131	44,593.896	45,654.996	46,765.495	47,865.349	2011
111	USA	NGDPPC	United States	Gross domestic product per capita, current prices	GDP is expressed in current national currency per person. Data are derived by dividing current price GDP by total population.	National currency	Units	See notes for:  Gross domestic product, current prices (National currency) Population (Persons).	12,249.040	13,599.987	14,014.584	15,089.233	16,634.805	17,689.601	18,537.764	19,511.165	20,820.823	22,169.176	23,197.700	23,647.566	24,699.626	25,629.125	26,906.527	27,826.601	29,076.547	30,541.333	31,857.839	33,501.684	35,251.927	36,064.520	36,949.993	38,324.553	40,401.197	42,628.552	44,750.288	46,467.466	46,900.905	45,461.429	46,811.195	48,327.861	49,802.148	51,056.461	52,804.658	54,952.135	57,338.527	59,916.496	2011
111	USA	NGDPDPC	United States	Gross domestic product per capita, current prices	GDP is expressed in current U.S. dollars per person. Data are derived by first converting GDP in national currency to U.S. dollars and then dividing it by total population.	U.S. dollars	Units	See notes for:  Gross domestic product, current prices (National currency) Population (Persons).	12,249.040	13,599.987	14,014.584	15,089.233	16,634.805	17,689.601	18,537.764	19,511.165	20,820.823	22,169.176	23,197.700	23,647.566	24,699.626	25,629.125	26,906.527	27,826.601	29,076.547	30,541.333	31,857.839	33,501.684	35,251.927	36,064.520	36,949.993	38,324.553	40,401.197	42,628.552	44,750.288	46,467.466	46,900.905	45,461.429	46,811.195	48,327.861	49,802.148	51,056.461	52,804.658	54,952.135	57,338.527	59,916.496	2011
111	USA	NGAP_NPGDP	United States	Output gap in percent of potential GDP	Output gaps for advanced economies are calculated as actual GDP less potential GDP as a percent of potential GDP. Estimates of output gaps are subject to a significant margin of uncertainty. For a discussion of approaches to calculating potential output, see Paula R. De Masi, IMF Estimates of Potential Output: Theory and Practice, in Staff Studies for the World Economic Outlook (Washington: IMF, December 1997), pp. 40-46.	Percent of potential GDP		See notes for:  Gross domestic product, constant prices (National currency).	-1.997	-1.117	-5.788	-4.386	-0.514	0.158	0.216	0.295	1.304	1.866	0.747	-2.160	-1.370	-1.156	0.067	-0.292	0.347	1.607	2.494	3.753	4.356	1.591	0.138	-0.078	0.546	1.348	1.787	1.409	-0.939	-5.559	-4.475	-4.377	-4.059	-3.967	-3.192	-2.170	-1.153	-0.209	2011