Message-ID: <6E8D8DFDE5FA5D4ABCB8508389D1BF88FFAADF55@SRVEXCHCM301.precheza.cz>
Date: 2017-09-08T09:25:01Z
From: PIKAL Petr
Subject: Optimize code to read text-file with digits
In-Reply-To: <CAGAA5bcyLFRwcEz+kQOazQnEae_KEASp9S8jC38X8SZPMUhMww@mail.gmail.com>
Hi
see in line
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Martin
> Moller Skarbiniks Pedersen
> Sent: Friday, September 8, 2017 10:49 AM
> To: r-help at r-project.org
> Subject: [R] Optimize code to read text-file with digits
>
> Hi,
>
> Every day I try to write some small R programs to improve my R-skills.
> Yesterday I wrote a small program to read the digits from "A Million Random
> Digits" from RAND.
> My code works but it is very slow and I guess the code is not optimal.
>
> The digits.txt file downloaded from
> https://www.rand.org/pubs/monograph_reports/MR1418.html
> contains 20000 lines which looks like this:
> 00000 10097 32533 76520 13586 34673 54876 80959 09117 39292 74945
> 00001 37542 04805 64894 74296 24805 24037 20636 10402 00822 91665
> 00002 08422 68953 19645 09303 23209 02560 15953 34764 35080 33606
> 00003 99019 02529 09376 70715 38311 31165 88676 74397 04436 27659
> 00004 12807 99970 80157 36147 64032 36653 98951 16877 12171 76833
>
> My program which is slow looks like this:
>
> filename <- "digits.txt"
> lines <- readLines(filename)
why you do not read a file as a whole e.g. by
lines<-read.table("digits.txt")
After that you do not need for cycle (but maybe I misunderstand what you really want)
remove first column
lines <- lines[,-1]
And now I am lost.
Do you want each row convert into a numeric vector? It probably exceed the precision of biggest number allowed.
Do you want to split each column to 5 numeric columns?
you can use something like
outer(lines[,1], 10^c(4:0), function(a, b) a %/% b %% 10)
to split the first column.
Or do you want one big numeric vector from all your numbers?
here you need to read values as character variables
lines<-read.table("digits.txt", colClasses="character")
numbers<-as.numeric(unlist(strsplit(as.character(lines[1,]),"")))
changes first row to numeric vector.
Anyway, can you explain what is your final goal?
Cheers
Petr
>
> numbers <- vector('numeric')
> for (i in 1:length(lines)) {
>
> # remove first column
> lines[i] <- sub("[^ ]+ +","",lines[i])
>
> # remove spaces
> lines[i] <- gsub(" ","",lines[i])
>
> # split the characters and convert them into numbers
> numbers <- c(numbers,as.numeric(unlist(strsplit(lines[i],""))))
> }
>
> Thanks for any advice how this program can be improved.
>
> Regards
> Martin M. S. Pedersen
>
> [[alternative HTML version deleted]]
>
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