unicode characters conversion in R

Question

I have this MTST column, which when printed yields

 [1] "<U+0391>G<U+03A1><U+0399><U+039D><U+0399><U+039F>                                 "
 [2] "<U+0391>G<U+03A7><U+0399><U+0391><U+039B><U+039F>S                                "
 [3] "<U+0391><U+0399>G<U+0399><U+039D><U+0391>                                  "
 [4] "<U+0391><U+0399>G<U+0399><U+039F>                                   "
 [5] "<U+0391><U+0399><U+0394><U+0397><U+03A8><U+039F>S                                 "
 [6] "<U+0391><U+039A><U+03A4><U+0399><U+039F>(<U+03A0><U+03A1><U+0395><U+0392><U+0395><U+0396><U+0391>)                          "
 [7] "<U+0391><U+039B><U+0395><U+039E><U+0391><U+039D><U+0394><U+03A1><U+039F><U+03A5><U+03A0><U+039F><U+039B><U+0397>                          "
 [8] "<U+0391><U+039B><U+0399><U+0391><U+03A1><U+03A4><U+039F>S                                "

I tried using Unicode library and do MTST<- as.u_char(MTST) that gives

[1] <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>

I've also tried dump and dput but nothing changed.

Note that MTST is initially of type character.

Appreciate your help. Thanks

edit: below dput(MTST) is shown

c("<U+0391>G<U+03A1><U+0399><U+039D><U+0399><U+039F>                                 ",
"<U+0391>G<U+03A7><U+0399><U+0391><U+039B><U+039F>S                                ",
"<U+0391><U+0399>G<U+0399><U+039D><U+0391>                                  ",
"<U+0391><U+0399>G<U+0399><U+039F>                                   ",
"<U+0391><U+0399><U+0394><U+0397><U+03A8><U+039F>S                                 ",
"<U+0391><U+039A><U+03A4><U+0399><U+039F>(<U+03A0><U+03A1><U+0395><U+0392><U+0395><U+0396><U+0391>)                          ",
"<U+0391><U+039B><U+0395><U+039E><U+0391><U+039D><U+0394><U+03A1><U+039F><U+03A5><U+03A0><U+039F><U+039B><U+0397>                          ",
"<U+0391><U+039B><U+0399><U+0391><U+03A1><U+03A4><U+039F>S                                ",
"<U+0391><U+039D><U+0391><U+0392><U+03A1><U+03A5><U+03A4><U+0391>                                ",
"<U+0391><U+039D><U+0394><U+03A1><U+0391><U+0392><U+0399><U+0394><U+0391>                               ",
"<U+0391><U+039D>OG<U+0395><U+0399><U+0391>                                 ",
"<U+0391><U+03A1><U+0391><U+039E><U+039F>S                                  ",
"<U+0391><U+03A1><U+0391><U+03A7>O<U+0392><U+0391>                                 ",
"<U+0391><U+03A1>G<U+039F>S(<U+03A0><U+03A5><U+03A1>G<U+0395><U+039B><U+0391>)                          ",
"<U+0391><U+03A1>G<U+039F>S<U+03A4><U+039F><U+039B><U+0399>                               ",
"<U+0391><U+03A1><U+03A4><U+0391> (<U+03A0><U+039F><U+039B><U+0397>)                             ",
"<U+0391><U+03A1><U+03A4><U+0391> (F<U+0399><U+039B><U+039F>T<U+0395><U+0397>)                          ",
"<U+0391>S<U+03A4><U+0395><U+03A1><U+039F>S<U+039A><U+039F><U+03A0><U+0395><U+0399><U+039F>                           ",
"<U+0391>S<U+03A4><U+03A1><U+039F>S                                  ",
"<U+0391>S<U+03A4><U+03A5><U+03A0><U+0391><U+039B><U+0391><U+0399><U+0391>                              ",
"<U+0392><U+0391><U+039C><U+039F>S                                   ",
"<U+0392><U+0395><U+039B><U+039F> (<U+039A><U+039F><U+03A1><U+0399><U+039D>T<U+0399><U+0391>S)                        ",
"<U+0392><U+039F><U+039B><U+039F>S                                   ",
"<U+0392><U+03A5><U+03A4><U+0399><U+039D><U+0391>                                  ",
"G<U+039F><U+03A1><U+03A4><U+03A5>S                                  ",
"G<U+03A5>T<U+0395><U+0399><U+039F>                                  ",
"<U+0394><U+0395>SF<U+0399><U+039D><U+0391>                                 ",
"<U+0394><U+0399><U+0391><U+0392><U+039F><U+039B><U+0399><U+03A4>S<U+0399>                              ",
"<U+0394><U+039F><U+039C><U+039F><U+039A><U+039F>S                                 ",
"<U+0394><U+03A1><U+0391><U+039C><U+0391>                                   ",
"<U+0395><U+0394><U+0395>SS<U+0391>                                  ",
"<U+0395><U+039B><U+0395><U+03A5>S<U+0399><U+039D><U+0391>                                ",
"<U+0395><U+039B><U+039B><U+0397><U+039D><U+0399><U+039A><U+039F> ae<U+03C1>                            ",
"<U+0396><U+0391><U+039A><U+03A5><U+039D>T<U+039F>S                                ",
"<U+0396><U+0391><U+039A><U+03A5><U+039D>T<U+039F>S_<U+03A0><U+039F><U+039B><U+0397>                           ",
"<U+0396><U+0391><U+03A1><U+039F>S                                   ",
"<U+0397><U+03A1><U+0391><U+039A><U+039B><U+0395><U+0399><U+039F>                                ",
"T<U+0391>S<U+039F>S                                   ", "T<U+0397><U+03A1><U+0391> (S<U+0391><U+039D><U+03A4><U+039F><U+03A1><U+0399><U+039D><U+0397>",
"<U+0399><U+0395><U+03A1><U+0391><U+03A0><U+0395><U+03A4><U+03A1><U+0391>                               ",
"<U+0399><U+039A><U+0391><U+03A1><U+0399><U+0391>_<U+0391>/<U+0394>                              ",
"<U+0399>O<U+0391><U+039D><U+039D><U+0399><U+039D><U+0391>                                ",
"<U+039A><U+0391><U+0392><U+0391><U+039B><U+0391> (<U+03A0><U+039F><U+039B><U+0397>)                           ",
"<U+039A><U+0391><U+0392><U+0391><U+039B><U+0391>(<U+0391><U+039C><U+03A5>G<U+0394><U+0391><U+039B><U+0395>O<U+039D><U+0391>S)                    ",
"<U+039A><U+0391><U+039B><U+0391><U+0392><U+03A1><U+03A5><U+03A4><U+0391>                               ",
"<U+039A><U+0391><U+039B><U+0391><U+039C><U+0391><U+03A4><U+0391>                                ",
"<U+039A><U+0391><U+039B><U+0391><U+039C><U+03A0><U+0391><U+039A><U+0391>                               ",
"<U+039A><U+0391><U+03A1><U+0394><U+0399><U+03A4>S<U+0391>                                ",
"<U+039A><U+0391><U+03A1><U+03A0><U+0391>T<U+039F>S_<U+0391>/<U+0394>                            ",
"<U+039A><U+0391><U+03A1><U+03A0><U+0391>T<U+039F>S_<U+03A0><U+039F><U+039B><U+0397>                           ",
"<U+039A><U+0391><U+03A1><U+03A0><U+0395><U+039D><U+0397>S<U+0399>                               ",
"<U+039A><U+0391><U+03A1><U+03A5>S<U+03A4><U+039F>S                                ",
"<U+039A><U+0391>S<U+039F>S                                   ",
"<U+039A><U+0391>S<U+03A4><U+0395><U+039B><U+039B><U+0399>                                ",
"<U+039A><U+0391>S<U+03A4><U+039F><U+03A1><U+0399><U+0391>                                ",
"<U+039A><U+0395><U+03A1><U+039A><U+03A5><U+03A1><U+0391>                                 ",
"<U+039A><U+039F><U+0396><U+0391><U+039D><U+0397>                                  ",
"<U+039A><U+039F><U+039C><U+039F><U+03A4><U+0397><U+039D><U+0397>                                ",
"<U+039A><U+039F><U+039D><U+0399><U+03A4>S<U+0391>                                 ",
"<U+039A><U+039F><U+03A1><U+0399><U+039D>T<U+039F>S                                ",
"<U+039A><U+03A5>T<U+0397><U+03A1><U+0391>_<U+0391>/<U+0394>                              ",
"<U+039A><U+03A5><U+039C><U+0397>                                    ",
"<U+039A>OS                                     ", "<U+039A>OS_<U+03A0><U+039F><U+039B><U+0397>                                ",
"<U+039B><U+0391><U+039C><U+0399><U+0391>                                   ",
"<U+039B><U+0391><U+03A1><U+0399>S<U+0391>                                  ",
"<U+039B><U+0395><U+03A1><U+039F>S                                   ",
"<U+039B><U+0395><U+03A5><U+039A><U+0391><U+0394><U+0391> (<U+039D><U+0397>S<U+0399>)                          ",
"<U+039B><U+0395>O<U+039D><U+0399><U+0394><U+0399><U+039F>                                ",
"<U+039B><U+0397><U+039C><U+039D><U+039F>S                                  ",
"<U+039B><U+0399><U+0394>O<U+03A1><U+0399><U+039A><U+0399>                                ",
"<U+039C><U+0391><U+039A><U+0395><U+0394><U+039F><U+039D><U+0399><U+0391>                               ",
"<U+039C><U+0391><U+03A1><U+0391>TO<U+039D><U+0391>S                               ",
"<U+039C><U+0395>TO<U+039D><U+0397>                                  ",
"<U+039C><U+0395>S<U+039F><U+039B><U+039F>GG<U+0399>                               ",
"<U+039C><U+0397><U+039B><U+039F>S_<U+0391><U+039C>S           

Answer 1

What you have there looks like plain 7-bit ASCII characters with some attempt at encoding Unicode code-points by wrapping some of them thus: <U+abcd>.

This is not a recognised encoding for Unicode, as far as I can tell, partly because how would you put a real < in your text? I suppose every < could be <U+jklm> where jklm is the code for an angle bracket... But ick.

So, first, try and get a UTF-8 encoded string from whatever generated this ascii-encoded mess!

However... after some serious hair pulling...

stringi to the rescue! Where 'MTST' is your vector of stuff, first convert the angle bracket notation to backslash-u and then use stri_unescape_unicode:

> require(stringi)
> greek2=gsub(">","", gsub("<U\+","\\u",MTST))
> stri_unescape_unicode(greek2)
[1] "ΑGΡΙΝΙΟ                                 "
[2] "ΑGΧΙΑΛΟS                                "
[3] "ΑΙGΙΝΑ                                  "
[4] "ΑΙGΙΟ                                   "
[5] "ΑΙΔΗΨΟS                                 "
[6] "ΑΚΤΙΟ(ΠΡΕΒΕΖΑ)                          "

all the way up to

[123] "FΥΧΤΙΑ                                  "
[124] "ΧΑΛΚΙΔΑ                                 "
[125] "ΧΑΝΙΑ                                   "
[126] "ΧΙΟS                                    "
[127] "ΧΡΥSΟΥΠΟΛΗ_ΚΑΒΑΛΑ                       "
[128] "OΡΕΟΙ                                   "

once I fixed the bizarrely missing comma and quote mark in your "dput" data (edited your question for you).