editing sentence start <s> and end </s> with R for prediction

Question

I'm building an NLP model to predict the next word in R. So, for a 3 sentences corpus:

a<-"i like cheese"

b<-"the dog like cat"

c<-"the cat eat cheese"

I want it to become:

>a
 "<.s> i like cheese <./s>"

>b
 "<.s> the dog like cat <./s>"

>c
 "<.s> the cat eat cheese <./s>"

Is there a simpler way to do this than:

a<-Unlist(strsplit(a, " "))
a[1]<-"<.s>"
a[length(a)]<-"./s>"
a<-paste(a, collapse = " ")
> a 
 "<.s> i like cheese <./s>"

Answer 1

您只是连接字符串，所以这应该可以工作：

 a <- paste("<.s>", a, "<./s>")