[R] Optimize code to read text-file with digits

[PIKAL Petr]

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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