data.table Cross Join In R


    Original Post

    data.table Cross Join In R

    Original Post

    〈data.table Cross Join In R〉



    data.table is a popular library in R, powerful, efficient. But the join/merge syntaxes in data.table are not so straightforward.
    The common syntax as below which referred  〈JOINing data in R using data.table〉.


    Join TypeDTdata.table::merge()
    InnerX[Y, nomatch = 0]merge(X, Y, all=FALSE)
    Left OuterY[X]merge(X, Y, all.x=TRUE)
    Right Outermerge(X, Y, all.y=TRUE)
    Full Outermerge(X, Y, all=TRUE)
    Full Outer Where Null (Not Inner)merge(X, Y, all=TRUE)
    Cross Join


    How About Cross Join?

    Cross join is a method in SQL. This method will cause data quantity to increase significantly, but it is extremely helpful in the right case.




    Copy, Paste, And Work

    Add the function to your codebase to upgrade your programming efficiency.


    dt_cross_join <- function(a, b){  
      cj = CJ(1:nrow(a),1:nrow(b))


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

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