[R] Analysing Character Strings for subsequent frequency analysis

[bob stoner]

Hi
I'm trying to get to grips with R and establish R as a teaching medium 
in my secondary school. I would like to use R to analyse text so I can 
produce frequency analysis of the text for subsequent examination of 
ciphers. I can produce code in VBA but I am struggling when writing in R 
to examine each character. There must be a clear method using the 
vectorised format of R. Furthermore, how do you substr a text string and 
reference each letter? I can use nchar to see how many letters per 
string but not to select each letter. I would prefer to remain in R and 
not deviate to Python etc as getting R onto the school mainframe has 
been a long journey...
Many thanks

Bob Stoner
Sleaford, Lincolnshire, UK