sorting - Keeping multiple orders in data.table in R -


i have transaction table 50m rows, few sample fields follow:

buyer_id  month day hour location seller_id

i need repeatedly sort table find popular sellers, locations, month etc. per buyer , create new summary table.

i need merge summary table transaction table find out sellers popular in top frequent locations etc.

each time, i'll have re-sort transaction table according several sets of columns. might end sorting setorder(transaction, user_id, month, location) several times.

i know data.table create order reference (kinda keep in hidden column), without copying table.

is there way store , refer these "hidden columns" explicitly, don't have resort data many times in same way?


Comments

Post a Comment

Popular posts from this blog

IF statement in MySQL trigger -

this query code in mysql trigger. if 1=2 select 'yes'; else select 'no'; end if; but has following error: if '1'='2' select 'yes' error code: 1064. have error in sql syntax; check manual corresponds mysql server version right syntax use near 'if '1'='2' select 'yes'' @ line 1 0.000 sec what solution?
Read more

c++ - What does MSC in "// appease MSC" comments mean? -

i run across // appease msc in c++ comments, e.g. here : const int& array::operator[](int offset) const { int mysize = getitssize(); if (offset >= 0 && offset < getitssize()) return ptype[offset]; throw xboundary(); return ptype[offset]; // appease msc! } what msc stand ? the author means microsoft's compiler, more formally known msvc.
Read more

android - MPAndroidChart - How to add Annotations or images to the chart -

i working latest mpandroidchart library , looking way add annotations or images clickable. example: once data reaches value event occurs want able display user - there multiple events can occur annotations (not sure if right word) or image added @ point in chart. any pointers welcome. check documentation of yaxis . focus on setspacetop(...) , setaxismaxvalue(...) methods. for background: bar-shadow , disable calling: barchart.setdrawbarshadow(false) or change color: bardataset.setbarshadowcolor(int color)
Read more