Hi all,
After reading this interesting discussion I delved a bit deeper into the
subject matter. The following snippet of code (see the end of my mail)
compares three ways of performing this task, using ddply, ave and one
yet unmentioned option: data.table (a package). The piece of code
Hello there,
Im computing the total value of an order from the price of the order items
using a for loop and the ifelse function. I do this on a large dataframe
(close to 1m lines). The computation of this function is painfully slow: in
1min only about 90 rows are calculated.
The
Verzonden: woensdag 3 augustus 2011 15:26
Aan: r-help@r-project.org
Onderwerp: [R] slow computation of functions over large datasets
Hello there,
I'm computing the total value of an order from the price of the order items
using
a for loop and the ifelse function. I do this on a large dataframe
On Aug 3, 2011, at 9:25 AM, Caroline Faisst wrote:
Hello there,
Im computing the total value of an order from the price of the
order items
using a for loop and the ifelse function.
Ouch. Schools really should stop teaching SAS and BASIC as a first
language.
I do this on a
.
--
david.
Best regards,
Thierry
-Oorspronkelijk bericht-
Van: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org
]
Namens Caroline Faisst
Verzonden: woensdag 3 augustus 2011 15:26
Aan: r-help@r-project.org
Onderwerp: [R] slow computation of functions over large datasets
Hello
This takes about 2 secs for 1M rows:
n - 100
exampledata - data.frame(orderID = sample(floor(n / 5), n, replace = TRUE),
itemPrice = rpois(n, 10))
require(data.table)
# convert to data.table
ed.dt - data.table(exampledata)
system.time(result - ed.dt[
+ ,
On Aug 3, 2011, at 12:20 PM, jim holtman wrote:
This takes about 2 secs for 1M rows:
n - 100
exampledata - data.frame(orderID = sample(floor(n / 5), n, replace
= TRUE), itemPrice = rpois(n, 10))
require(data.table)
# convert to data.table
ed.dt - data.table(exampledata)
On Aug 3, 2011, at 2:01 PM, Ken wrote:
Hello,
Perhaps transpose the table attach(as.data.frame(t(data))) and use
ColSums() function with order id as header.
-Ken Hutchison
Got any code? The OP offered a reproducible example, after all.
--
David.
On Aug 3, 2554 BE, at 1:12
Sorry about the lack of code, but using Davids example, would:
tapply(itemPrice, INDEX=orderID, FUN=sum)
work?
-Ken Hutchison
On Aug 3, 2554 BE, at 2:09 PM, David Winsemius dwinsem...@comcast.net wrote:
On Aug 3, 2011, at 2:01 PM, Ken wrote:
Hello,
Perhaps transpose the table
Hello,
Perhaps transpose the table attach(as.data.frame(t(data))) and use ColSums()
function with order id as header.
-Ken Hutchison
On Aug 3, 2554 BE, at 1:12 PM, David Winsemius dwinsem...@comcast.net wrote:
On Aug 3, 2011, at 12:20 PM, jim holtman wrote:
This takes
On Aug 3, 2011, at 3:05 PM, Ken wrote:
Sorry about the lack of code, but using Davids example, would:
tapply(itemPrice, INDEX=orderID, FUN=sum)
work?
Doesn't do the cumulative sums or the assignment into column of the
same data.frame. That's why I used ave, because it keeps the sequence
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