data.table Advanced Technics And Examples | Data Science With R

Outline

    Original Post

    data.table Advanced Technics And Examples | Data Science With R


    Original Post

    data.table Advanced Technics And Examples | Data Science With R


    data.table是R語言的熱門套件,能夠快速處理大量資料,效率高於dplyr,且得利於語法結構的精巧設計,data.table更容易寫出版排整齊的程式。這篇文章會討論data.table的進階技巧,在Cheat Sheat上也不一定找得到。

    .GRP – Add index for each group

    dt <- data.table(C1 = c("A", "B", "C", "B", "A"),
                     C2 = c(1, 2, 3, 2, 1))
    
    dt2 <- dt[, INDEX := .GRP, by = .(C1)]
       C1 C2 INDEX
    1:  A  1     1
    2:  B  2     2
    3:  C  3     3
    4:  B  2     2
    5:  A  1     1

    Subset with row index and column index

    dt <- data.table(C1 = 1:3,
                     C2 = 101:103,
                     C3 = 901:903)
    
    dt_row <- dt[1:2, ]
    dt_col <- dt[, 2:3]
    dt_row_col <- dt[1:2, 2:3]
    > dt_row
       C1  C2  C3
    1:  1 101 901
    2:  2 102 902
    > dt_col
        C2  C3
    1: 101 901
    2: 102 902
    3: 103 903
    > dt_row_col
        C2  C3
    1: 101 901
    2: 102 902


    Related Posts

    Aron

    A data scientist working in a retail company, with experience in web design and marketing. Recently dives into cryptocurrency and quantitative investing.

    facebook telegram
    Content Protection by DMCA.com

    Leave a Reply

    • Required fields are market * .
    • Your email address will not be published.
    • Please ensure your email address is correct, then you will get a notification once a new comment reply.

    Your email address will not be published. Required fields are marked *