R help - Jun 2013 - splitting a string column into multiple columns faster

Hello!

I have a column in my data frame that I have to split: I have to distill
the numbers from the text. Below is my example and my solution.

x<-data.frame(x=c("aaa1_bbb1_ccc3","aaa2_bbb3_ccc2","aaa3_bbb2_ccc1"))
x
library(stringr)
out<-as.data.frame(str_split_fixed(x$x,"aaa",2))
out2<-as.data.frame(str_split_fixed(out$V2,"_bbb",2))
out3<-as.data.frame(str_split_fixed(out2$V2,"_ccc",2))
result<-cbind(x,out2[1],out3)
result
My problem is:
str_split.fixed is relatively slow. In my real data frame I have over
80,000 rows so that it takes almost 30 seconds to run just one line (like
out<-... above)
And it's even slower because I have to do it step-by-step many times.

Any way to do it by specifying all 3 delimiters at once
("aaa","_bbb","_ccc") and then split it in one
swoop into a data frame with
several columns?

Thanks a lot for any pointers!

-- 
Dimitri Liakhovitski

	[[alternative HTML version deleted]]

HI,
May be this helps:

res<-data.frame(x=x,read.table(text=gsub("[A-Za-z]","",x[,1]),sep="_",header=FALSE),stringsAsFactors=FALSE)
res
#?????????????? x V1 V2 V3
#1 aaa1_bbb1_ccc3? 1? 1? 3
#2 aaa2_bbb3_ccc2? 2? 3? 2
#3 aaa3_bbb2_ccc1? 3? 2? 1
A.K.

----- Original Message -----
From: Dimitri Liakhovitski <dimitri.liakhovitski at gmail.com>
To: r-help <r-help at r-project.org>
Cc: 
Sent: Friday, June 7, 2013 9:24 PM
Subject: [R] splitting a string column into multiple columns faster

Hello!

I have a column in my data frame that I have to split: I have to distill
the numbers from the text. Below is my example and my solution.

x<-data.frame(x=c("aaa1_bbb1_ccc3","aaa2_bbb3_ccc2","aaa3_bbb2_ccc1"))
x
library(stringr)
out<-as.data.frame(str_split_fixed(x$x,"aaa",2))
out2<-as.data.frame(str_split_fixed(out$V2,"_bbb",2))
out3<-as.data.frame(str_split_fixed(out2$V2,"_ccc",2))
result<-cbind(x,out2[1],out3)
result
My problem is:
str_split.fixed is relatively slow. In my real data frame I have over
80,000 rows so that it takes almost 30 seconds to run just one line (like
out<-... above)
And it's even slower because I have to do it step-by-step many times.

Any way to do it by specifying all 3 delimiters at once
("aaa","_bbb","_ccc") and then split it in one
swoop into a data frame with
several columns?

Thanks a lot for any pointers!

-- 
Dimitri Liakhovitski

??? [[alternative HTML version deleted]]

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