[R] Problem with greek characters in R

[Dimitrios Mousenikas]

Hello,

My computer functions with the version of English windows 10. The problem that I face is that when I open an R file that includes Greek characters, with the program RGui, the text that appears does not make sense. The only way the problem can be solved is by setting Greek as a default language in Windows. Although I prefer as a default language English. 
I am looking forward for your response. 

Thank you in advance
Dimitrios Mousenikas