R - Extract strings based on pattern

We can try functions from tidyverse:

library(tidyverse)
str_split_fixed(vec, pattern = " ", n = 3) %>% 
  as.data.frame() %>%
  mutate(V3 = str_sub(V3,3,-2)) %>%
  separate(V3, c("V3", "V4"), sep = ", ")

The code is written as follows:

1. Split vector vec by a space into 3 columns and coerce it as a dataframe.
2. Extract strings from the 3rd column to exclude open and close brackets and "w".
3. Separate the 3rd column by ", ".

An example of the output:

   V1    V2            V3         V4
1 Tue 12-14           1-6      CLB 6
2 Mon 18-20           1-6 ColomboThC
3 Thu 14-16 1-6,7-9,10-12      CLB 8

Using the input x in the Note at the end:

• replace the first space in each string with a semicolon,
• replace the next space and its following two characters with semicolon,
• replace the next occurrence of comma space with semicolon
• remove the last character
• read that into a data frame splitting fields at semicolons
• split the 3rd column into a list of character vectors using commas -- omit this step if you prefer to have character string rather than list as 3rd column

It uses only individually simple steps and no packages.

y <- x
y <- sub(" ", ";", y)
y <- sub(" ..", ";", y)
y <- sub(", ", ";", y)
y <- sub(".$", "", y)
DF <- read.table(text = y, sep = ";", as.is = TRUE, fill = NA)
DF[[3]] <- strsplit(DF[[3]], ",")

giving:

> DF
    V1    V2              V3         V4
1  Tue 12-14             1-6      CLB 6
2  Mon 18-20             1-6 ColomboThC
3  Thu 14-16 1-6, 7-9, 10-12      CLB 8
4  Fri    13      2-9, 10-13    Law 388
5  Fri    14      2-9, 10-13 Sqhouse206
6  Fri    15      2-9, 10-13 Sqhouse115
7  Thu    17      2-9, 10-13  Block G16
8  Thu    18      2-9, 10-13  Block G16
9  Mon    10      2-9, 10-13 AinswthG01
10 Mon    11      2-9, 10-13 Sqhouse203
11 Mon    12      2-9, 10-13 Sqhouse206
12 Mon    13      2-9, 10-13    BUS 114
13 Mon    16      2-9, 10-13   Gold G03
14 Mon    17      2-9, 10-13  Quad G047
15 Mon    20      2-9, 10-13   Col LG02
16 Tue    17      2-9, 10-13  Quad 1001
17 Tue    18      2-9, 10-13  Quad 1001
18 Tue    19      2-9, 10-13  Quad 1001
19 Tue    20      2-9, 10-13           
20 Wed    10      2-9, 10-13  Quad 1046
21 Wed    11      2-9, 10-13  Quad 1046

It would be possible to replace the first 4 lines of code with this one line in which case it reduces to only 4 lines of code in total.

y <- Reduce(function(x, pat) sub(pat, ";", x), init = x, c(" ", " ..", ", "))

Note: The input x in reproducible form is:

x <- c("Tue 12-14 (w1-6, CLB 6)", "Mon 18-20 (w1-6, ColomboThC)", 
"Thu 14-16 (w1-6,7-9,10-12, CLB 8)", "Fri 13 (w2-9,10-13, Law 388)", 
"Fri 14 (w2-9,10-13, Sqhouse206)", "Fri 15 (w2-9,10-13, Sqhouse115)", 
"Thu 17 (w2-9,10-13, Block G16)", "Thu 18 (w2-9,10-13, Block G16)", 
"Mon 10 (w2-9,10-13, AinswthG01)", "Mon 11 (w2-9,10-13, Sqhouse203)", 
"Mon 12 (w2-9,10-13, Sqhouse206)", "Mon 13 (w2-9,10-13, BUS 114)", 
"Mon 16 (w2-9,10-13, Gold G03)", "Mon 17 (w2-9,10-13, Quad G047)", 
"Mon 20 (w2-9,10-13, Col LG02)", "Tue 17 (w2-9,10-13, Quad 1001)", 
"Tue 18 (w2-9,10-13, Quad 1001)", "Tue 19 (w2-9,10-13, Quad 1001)", 
"Tue 20 (w2-9,10-13)", "Wed 10 (w2-9,10-13, Quad 1046)", "Wed 11 (w2-9,10-13, Quad 1046)", 
"Wed 12 (w2-9,10-13, Quad 1046)", "Wed 13 (w2-9,10-13, Quad G046)"

Base funciton can do, you don't need to import any other packages. tidyverse is great one but a little bit big for this,

x=c("Thu 18 (w2-9,10-13, Block G16)","Mon 18-20 (w1-6, ColomboThC)")
do.call(rbind,lapply(x,function(i){
  y=strsplit(i,' \\(')[[1]]
  y[2]=gsub('\\)','',y[2])
  out1=strsplit(y[1],' ')[[1]]
  out2=strsplit(y[2],', ')[[1]]
  listpart=grepl('-',out2)
  do.call(cbind,c(out1,list(out2[listpart]),out2[!listpart]))
}))

output will be:

         [,1]  [,2]    [,3]         [,4]        
[1,] "Thu" "18"    "w2-9,10-13" "Block G16" 
[2,] "Mon" "18-20" "w1-6"       "ColomboThC"