"\t"

Looks like someone intended to write a tab-separated file with \t and actually wrote a "custom" file format with /t. I would correct the file rather than trying to read it in as is.

I changed the backslash with a forwardslash. Now after executing the read.delim command as asked in the question , the head of the dataframe looks like this:

head(dataset4)
choc.tbeer.telec
1 1451\\t96.3\\t1497
2 2037\\t84.4\\t1463
3 2477\\t91.2\\t1648
4 2785\\t81.9\\t1595
5 2994\\t80.5\\t1777
6 2681\\t70.4\\t1824

With read.delim you do not need to specify the separator as tabulator is used by default. Try this:

dataset4 <- read.delim("./Documents/time_series/cbe.dat", colClasses = rep("numeric",3))

Should you file be separeted by \\t?

You could try changing the separator field to "\t". Try sed -i 's/\\t/\t/g' your_file. Do this in a copy of your file to test it!

can you try this hack with OP text?

df=read.csv("~/Desktop/test.txt", sep="t", strip.white = T)
data.frame(apply(df,2, function (x) gsub("[^0-9.-]","", x)))

output would be some thing like this:

 > data.frame(apply(df,2, function (x) gsub("[^0-9.-]","", x)))
   choc. beer. elec
1   1451  96.3 1497
2   2037  84.4 1463

Try following. It woorked.

library(magrittr)
readr::read_delim("inputfile.txt" ,delim = "\"/t\"")  %>%
dplyr::select("choc","beer" ,"elec") 


# A tibble: 20 x 3
    choc  beer  elec
   <dbl> <dbl> <dbl>
 1  1451  96.3  1497
 2  2037  84.4  1463
 3  2477  91.2  1648
 4  2785  81.9  1595
 5  2994  80.5  1777
 6  2681  70.4  1824
 7  3098  74.8  1994
 8  2708  75.9  1835
 9  2517  86.3  1787
10  2445  98.7  1699
11  2087 101.   1633
12  1801 114.   1645
13  1216  89.8  1597
14  2173  84.4  1577
15  2286  87.2  1709
16  3121  85.6  1756
17  3458  72    1936
18  3511  69.2  2052
19  3524  77.5  2105
20  2767  78.1  2016

^{Created on 2020-04-29 by the reprex package (v0.3.0)}