_       _ _(_)_     |  A fresh approach to technical computing
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  | | |_| | | | (_| |  |  Version 0.3.0-prerelease+490 (2013-12-15 07:16 UTC)
_/ |\__'_|_|_|\__'_|  |  Commit f8f3190* (0 days old master)
|__/                   |  x86_64-linux-gnu


julia> # load the package


julia> using DataFrames


julia> # read a txt file into dataframe


julia> df1 = readtable("credit_count.txt");


julia> # subset the dataframe


julia> df2 = df1[:(CARDHLDR .== 1), ["DEFAULT", "MAJORDRG", "MINORDRG"]];


julia> # aggregate the data


julia> df3 = by(df2, "DEFAULT", :(MAJOR_DRG = mean(_DF["MAJORDRG"])))
2x2 DataFrame:
        DEFAULT MAJOR_DRG
[1,]          0  0.139851
[2,]          1  0.175703




julia> df4 = by(df2, "DEFAULT", :(MINOR_DRG = mean(_DF["MINORDRG"])))
2x2 DataFrame:
        DEFAULT MINOR_DRG
[1,]          0  0.213196
[2,]          1  0.292169




julia> # join two dataframes


julia> df5 = join(df3, df4, on = "DEFAULT", kind = :inner)
2x3 DataFrame:
        DEFAULT MAJOR_DRG MINOR_DRG
[1,]          0  0.139851  0.213196
[2,]          1  0.175703  0.292169