Extracting word with co-occurring alphabets in R - r

Question

I wanted to extract certain words from a bigger word-list. One example of a desired extracted word-list is: extract all the words that contain /s/ followed by /r/. So this should give me words such as sər'ka:rəh, e:k'sa:r, səmʋitərəɳ, and so:'ha:rd. from the bigger word-list.
Consider the data (IPA transcription) to be the one given below:
sər'ka:rəh
sə'lᴔ:nija:
hã:ki:
pu:'dʒa:ẽ:
e:k'sa:r
mritko:
dʒʱã:sa:
pə'hũtʃ'ne:'ʋa:le:
kərəpʈ
tʃinhirit
tʃʰəʈʈʰi:
dʱũdʱ'la:pən
səmʋitərəɳ
so:'ha:rd
məl'ʈi:spe:'ʃijliʈi:
la:'pər'ʋa:i:
upləbɡʱ
Thanks much!

Answer 1

Here's an answer to the issue described in the first paragraph of your post. (To my mind, the examples in the second paragraph are inconsistent with the issue described in the first para, so I'll take the liberty of ignoring them here).
You say you want to "extract all the words that contain p followed by t". The word 'extract' implies that there are other characters in the same string than those you want to match and extract. The verb 'contain' implies that the words you want to extract need not necessarily have p in word-initial position. Based on these premises, here's some mock data and a solution to the task:
Data:
x <- c("pastry is to the pastor's appetite what pot is to the pupil's")
Solution:
libary(stringr)
unlist(str_extract_all(x, "\\b\\w*(?<=p)\\w*t\\w*\\b"))
This uses word boundaries \\b to extract the target words from the surrounding context; it further uses positive lookbehind (?<=...) to assert the condition that for there to be a matching t there needs to be a p character occurring prior to the match.
The regex in more detail:
\\b: the opening word boundary
\\w*: zero or more alphanumeric chars (or an underscore)
(?<=p): positive lookbehind: "if and only if you see a p char on
the left..."
\\w*: zero or more alphanumeric chars (or an underscore)
t: the literal character t
\\w*: zero or more alphanumeric chars (or an underscore)
\\b: the closing word boundary
Result:
[1] "pastry" "pastor" "appetite" "pot"
EDIT 1:
Now that the question has been updated, a more definitive answer is possible.
Data:
x <- c("sər'ka:rəh","sə'lᴔ:nija:","hã:ki:","pu:'dʒa:ẽ:","e:k'sa:r",
"mritko:","dʒʱã:sa:","pə'hũtʃ'ne:'ʋa:le:","kərəpʈ","tʃinhirit",
"tʃʰəʈʈʰi:","dʱũdʱ'la:pən","səmʋitərəɳ","so:'ha:rd",
"məl'ʈi:spe:'ʃijliʈi:", "la:'pər'ʋa:i:","upləbɡʱ")
If you want to match (rather than extract) words that "contain /s/ followed by /r/", you can use grepin various ways. Here are two ways:
grep("s.*r", x, value = T)
or:
grep("(?<=s).*r", x, value = T, perl = T) # with lookbehind
The result is the same in either case:
[1] "sər'ka:rəh" "e:k'sa:r" "səmʋitərəɳ" "so:'ha:rd"
EDIT 2:
If the aim is to match words that "contain /s/ or /p/ followed by /r/ or /t/", you can use the metacharacter | to allow for alternatives:
grep("s.*r|s.*t|p.*r|p.*t", x, value = T)
# or, more succinctly:
grep("(s|p).*(r|t)", x, value = T)
[1] "sər'ka:rəh" "e:k'sa:r" "pə'hũtʃ'ne:'ʋa:le:" "səmʋitərəɳ" "so:'ha:rd"
[6] "la:'pər'ʋa:i:"

Answer 2

You can use grep function. Assuming your list is called list:
grep("p[a-z]+t", list, value=TRUE)