r - Function for querying a data.table -


i have data.table called prices has 3 columns: ticker, date , price. have run

setkey(prices,ticker,date)

if code, works

prices[list("msft",as.date("2013-01-15")]

returning row msft in 2013-01-15 however, if write function

getprice <- function(ticker,date) {   prices[list(ticker,date)] }

it returns whole data.table suspect has scoping in parameter, can't work. how query data.table if don't know parameters in advance?

your problem variable names in function. change them e.g. x , y (so not same column names in data.table) , work. you're doing constructing data.table of ticker , date columns , joining that, recovering original data.

another (more robust) option smth in function:

getprice <- function(ticker,date) {   tmp = list(ticker, date)   prices[tmp] }

see faqs 2.12 , 2.13 more on - http://datatable.r-forge.r-project.org/datatable-faq.pdf


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