This is a tutorial about how to crawl the FRED big data in a rapid and methodical way
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A interactive linear tree figure of the category structure of the FRED is in the webpage, with the help of this blog  
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A round tree figure is in the webpage, with the help of the Observable notebook  
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A jupyter notebook of the strategy implemention. 
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Tree of the category crawler and json file generator 
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Download the top-10 popular data in the single thread way 
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Download the top-10 popular data in the multi thread way