The
ff package is a great and efficient way of working with large datasets.
One of the main reasons why I prefer to use it above other packages that allow working with large datasets is that it is a complete set of tools.
When comparing it to the other open source 'bigdata' packages in R
- It is not restricted to work basically with numeric data matrices like the bigmemory set of packages but allows relatively easy access to character vectors through factors
- It has efficient data loading functionality from flat/csv files, you can interact with SQL databases as explained here.
- You don't need to use the sqldf package to get and insert all the time your data in the right (RAM-limited) sized to and from an SQLite database
- It has higher level functionality (e.g. apply set of family, sorting, ...) which package mmap seems to be lacking
- And it allows you to work with datasets which you can not put in memory which the datatable package does not allow.
If you disagree, do comment.
In my dayly work, I encountered frequently that some bits are still missing in package ff to make it suited for easy day-to-day analysis of large data. Apparently I was not alone as Edwin de Jonge started already package
ffbase (available at
http://code.google.com/p/fffunctions/). For a predictive modelling project BNOSAC has made for
https://additionly.com/ we have made some nice progress in the package.
The package
ffbase now contains quite some extensions that are really usefull. It contains a lot of the functionality from the R's base package for usage with large datasets through package ff.
Namely
- Basic operations (c, unique, duplicated, ffmatch, ffdfmatch, %in%, is.na, all, any, cut, ffwhich, ffappend, ffdfappend)
- Standard operators (+, -, *, /, ^, %%, %/%, ==, !=, <, <=, >=, >, &, |, !) on ff vectors
- Math operators (abs, sign, sqrt, ceiling, floor, trunc, round, signif, log, log10, log2, log1p, exp, expm1, acos, acosh, asin, asinh, atan, atanh, cos, cosh, sin, sinh, tan, tanh, gamma, lgamma, digamma, trigamma)
- Selections & data manipulations (subset, transform, with, within, ffwhich)
- Summary statistics (sum, min, max, range, quantile, hist)
- Data transformations (cumsum, cumprod, cummin, cummax, table, tabulate, merge, ffdfdply)
These functions work all on either ff objects or objects of class ffdf from the
ff package
Next to that there are some extra goodies allowing faster grouping by - not restricted to the ff package alone (Fast groupwise aggregations: bySum, byMean, binned_sum, binned_sumsq, binned_tabulate)
This makes it a lot more easy to work with the ff package and large data.
Let me show some R-code to show what this means using a simple dataset of the Heritage Health Prize competition of only 2.6Mio records available for download for download here (
http://www.heritagehealthprize.com/c/hhp/data). It is a dataset with claims.
The code is for objects of ff/ffdf class and is based on version 0.6 of the package for download
here.
require(ffbase)
hhp <- read.table.ffdf(file="/home/jan/Work/RForgeBNOSAC/github/RBelgium_HeritageHealthPrize/Data/Claims.csv", FUN = "read.csv", na.strings = "")
class(hhp)
[1] "ffdf"
dim(hhp)
[1] 2668990 14
str(hhp[1:10,])
'data.frame': 10 obs. of 14 variables:
$ MemberID : int 42286978 97903248 2759427 73570559 11837054 45844561 99829076 54666321 60497718 72200595
$ ProviderID : int 8013252 3316066 2997752 7053364 7557061 1963488 6721023 9932074 363858 6251259
$ Vendor : int 172193 726296 140343 240043 496247 4042 265273 35565 293107 791272
$ PCP : int 37796 5300 91972 70119 68968 55823 91972 27294 64913 49465
$ Year : Factor w/ 3 levels "Y1","Y2","Y3": 1 3 3 3 2 3 1 1 2 3
$ Specialty : Factor w/ 12 levels "Anesthesiology",..: 12 5 5 6 12 10 11 2 11 5
$ PlaceSvc : Factor w/ 8 levels "Ambulance","Home",..: 5 5 5 3 7 5 5 5 5 5
$ PayDelay : Factor w/ 163 levels "0","10","101",..: 52 76 29 48 51 49 40 53 67 82
$ LengthOfStay : Factor w/ 10 levels "1 day","2- 4 weeks",..: NA NA NA NA NA NA NA NA NA NA
$ DSFS : Factor w/ 12 levels "0- 1 month","10-11 months",..: 11 10 1 8 7 6 1 1 4 10
$ PrimaryConditionGroup: Factor w/ 45 levels "AMI","APPCHOL",..: 26 26 21 21 10 26 38 33 19 22
$ CharlsonIndex : Factor w/ 4 levels "0","1-2","3-4",..: 1 2 1 2 2 1 1 1 1 2
$ ProcedureGroup : Factor w/ 17 levels "ANES","EM","MED",..: 3 2 2 7 2 2 3 5 2 7
$ SupLOS : int 0 0 0 0 0 0 0 0 0 0
## Some basic showoff
result <- list()
## Unique members, Unique combination of members and health care providers, find unexpected duplicated records
result$members <- unique(hhp$MemberID)
result$members.providers <- unique(hhp[c("MemberID","ProviderID")])
sum(duplicated(hhp[c("MemberID","ProviderID","Year","DSFS")]))
[1] 936859
## c operator
sum(duplicated(c(result$members, result$members))) # == length(result$members)
[1] 113000
## Basic example of operators is.na.ff, the ! operator and sum.ff
sum(!is.na(hhp$LengthOfStay))
[1] 71598
sum(is.na(hhp$LengthOfStay))
[1] 2597392
## all and any
any(is.na(hhp$LengthOfStay))
[1] TRUE
all(!is.na(hhp$PayDelay))
[1] TRUE
## Frequency table of Specialities and example of a 2-way table
result$speciality <- table.ff(hhp$Specialty, exclude=NA)
options(scipen = 1)
barplot(result$speciality[order(result$speciality)], col = "steelblue", horiz = FALSE, cex.names=0.6, main="Frequency table")
hhp$ProviderFactor <- with(data=hhp[c("ProviderID")], expr = as.character(ProviderID))
result$providerspeciality <- table.ff(hhp$Specialty, hhp$ProviderFactor, exclude=NA)
## Let's see if the member id's are uniformly distributed
hist(hhp$MemberID, col = "steelblue", main = "MemberID's histogram", xlab = "MemberID")
## %in% operator is overloaded
hhp$gp.laboratory <- hhp$Specialty %in% ff(factor(c("General Practice","Laboratory")))
hhp$gp.laboratory
ff (open) logical length=2668990 (2668990)
[1] [2] [3] [4] [5] [6] [7] [8]
FALSE FALSE FALSE TRUE FALSE FALSE FALSE FALSE
[2668983] [2668984] [2668985] [2668986] [2668987] [2668988] [2668989]
: FALSE TRUE FALSE FALSE FALSE FALSE FALSE
[2668990]
FALSE
## Some data cleaning
hhp$pdelay <- with(hhp[c("PayDelay")], as.numeric(PayDelay))
## Summary stats
mean(hhp$pdelay)
[1] 59.78436
range(hhp$pdelay)
[1] 1 163
quantile(hhp$pdelay)
0% 25% 50% 75% 100%
1 45 55 73 163
## cumsum
hist(cumsum.ff(hhp$pdelay), col = "steelblue")
max(cumsum.ff(hhp$pdelay))
[1] 159556245
## cut
table.ff(cut(hhp$pdelay, breaks = c(-Inf, 1, 10, 100, +Inf)), exclude=NA)
(-Inf,1] (1,10] (10,100] (100, Inf]
141451 46720 2237723 243096
## apply a function to a group of data - ddply type of logic from package plyr
hhp$MemberIDFactor <- with(data=hhp[c("MemberID")], expr = as.character(MemberID))
require(doBy)
result$delaybyperson <- ffdfdply(hhp[c("MemberID","pdelay")], split = hhp$MemberIDFactor, FUN=function(x){
summaryBy(pdelay ~ MemberID, data=x, FUN=sum, keep.names=FALSE)
}, trace=FALSE)
result$delaybyperson[1:5,]
MemberID pdelay.sum
1 18190 3158
2 20072 4915
3 20482 4189
4 21207 2548
5 32317 1064
## merging (in fact joining based on ffmatch or ffdfmatch)
hhp <- merge(hhp, result$delaybyperson, by = "MemberID", all.x=TRUE, all.y=FALSE)
names(hhp)
[1] "MemberID" "ProviderID" "Vendor"
[4] "PCP" "Year" "Specialty"
[7] "PlaceSvc" "PayDelay" "LengthOfStay"
[10] "DSFS" "PrimaryConditionGroup" "CharlsonIndex"
[13] "ProcedureGroup" "SupLOS" "ProviderFactor"
[16] "gp.laboratory" "pdelay" "MemberIDFactor"
[19] "pdelay.sum"
## Let's add a key (in version 0.6 of the package for download here)
hhp$key <- key(hhp[c("MemberID","ProviderID")])
max(hhp$key) == nrow(result$members.providers)
[1] TRUE
## A small example of operators
idx <- ffwhich(hhp[c("Specialty","PlaceSvc")], Specialty == "General Practice")
idx
ff (open) integer length=473655 (473655)
[1] [2] [3] [4] [5] [6] [7] [8]
18 19 20 31 35 42 45 62
[473648] [473649] [473650] [473651] [473652] [473653] [473654]
: 2668922 2668929 2668930 2668947 2668952 2668965 2668974
[473655]
2668984
hhp.gp <- hhp[idx, ]
class(hhp.gp)
[1] "ffdf"
nrow(hhp.gp)
[1] 473655
sum(is.na(idx))
[1] 0
sum(hhp$Specialty == "General Practice", na.rm=TRUE)
[1] 473655
## Or apply subset
table.ff(hhp$Year, exclude=NA)
Y1 Y2 Y3
865689 898872 904429
hhp.y1 <- subset(hhp, hhp$Year == "Y1")
nrow(hhp.y1)
[1] 865689
We welcome you to use the package if it suits your applications and if you have any requests, do post some comments to see how the package can be extended for your needs.
If you are into large data but not enormeoulsy big data everyone is talking about and you are tired of finding a solution to get your data with several 10's of millions of records in R without having RAM issues, having a look at the packages ff, ffbase and ETLUtils might be the solution to your problem.
Following up on
our post about the ETLUtils package which eases transferring large data from SQL databases to ffdf objects in R, the ETLUtils package has now been extended to include the function
read.odbc.ffdf which can be used to fetch your SQL queries on corporate Oracle, MySQL, PostgreSQL & sqlite databases.
Below we show an example where read.dbi.ffdf is used to fetch all rows of a table and we add data of the same structure with read.odbc.ffdf to the existing ffdf. This might be of interest to you if you work a lot with dayly incremental data updates.
The query below returned +/- 15Mio records using read.dbi.ffdf without any RAM issues (on this PC I have 4Gb of RAM) and added another 100000 records as an example using read.odbc.ffdf. And all of the data is completely in an ffdf in R.
require(ETLUtils)
login <- list()
login$user <- "bnosac"
login$password <- "YourPassword"
login$dbname <- "YourDB"
login$host <- "localhost/IPaddress"
require(RMySQL)
x <- read.dbi.ffdf(
query = "select * from semetis.keywords_performance_endofday", dbConnect.args = list(drv = dbDriver("MySQL"), dbname = login$dbname, user = login$user, password = login$password, host = login$host),
VERBOSE=TRUE)
1> dim(x)
[1] 14969674 27
login <- list()
login$dsn <- "YourDSN"
login$uid <- "bnosac"
login$pwd <- "YourPassword"
require(RODBC)
x <- read.odbc.ffdf(
query = "select * from semetis.keywords_performance_endofday where date = CURRENT_DATE-1", odbcConnect.args = list(dsn = login$dsn, uid = login$uid, pwd = login$pwd),
x = x,
VERBOSE=TRUE)
1> dim(x)
[1] 15062904 27
The ff package is great when you are working with large data in R. Data in corporate environments are usually not that large that a Hadoop system is needed to handle it but the data are mostly large enough to make R choke on it's RAM.
The ff package is great for this type of data. It can handle 2.14 billion elements per atomic (so 2.14 billion records). This is mostly more than enough in standard business settings nowadays.
For a while getting the data in R was quite cumbersome. The ff package now provides already nice interfaces to csv and flat files in the read.csv.ffdf and read.table.ffdf functions. To extend this towards standard SQL databases, the ETLUtils package has been put at CRAN. It contains a function called read.dbi.ffdf which can be used to extract easily data from any sql database through DBI directly into an ffdf in R.
Below, we show an example of importing a table stored at a MySQL database with 11.8 million records directly in an ffdf without having RAM issues.
The R package ETLUtils is now available for download at it's CRAN repository.
It's a package which facilitates the ETL in situations where you need to interact with SQL databases in a corporate environment. Basically it currently focusses on the E(Extract) part of the ETL.
In the libary you'll find a function called read.dbi.ffdf which allows to extract easily large datasets from an SQL database through DBI straight into a ffdf (part of the ff package). This should ease the usage of the ff package for working with large datasets in corporate environments where you need to interact e.g. with MySQL, PostgreSQL, Oracle through the package RMySQL, RPostgreSQL or ROracle without having to worry about RAM issues when importing large datasets.
