Strings can be combined using paste, paste0, and other utilities. When using paste, the default separator is space:

paste("I","think","therefore","I","am")

We can use a different separator by using the sep flag:

paste("I","think","therefore","I","am", sep="-")

paste0 is an extension of paste where the separator is null. As a result, all strings are concatenated into a single string unless separators are specified:

paste0("I","think","therefore","I","am") 

In addition to the sep flag, there is also a collapse flag that can be used to separate the results:

paste("grade",c("A","B","C"), sep=" ") # paste with separator space 
paste("grade",c("A","B","C"), sep=" ", collapse=",") # paste with separator space and collapse with "," (comma) 
paste0("grade",c("A","B","C"), collapse=",") # paste0 is set to the separator "" (null) 

The stringr package in R also contains several useful string manipulation functions. One of them, called str_c has been shown as follows:

library(stringr)  
str_c("grade",c("A","B","C",NULL)) # str_c from the stringr package is a newer (and somewhat simpler) alternative to paste/paste0 in R 
 

We can split the string using the following line of code:

strsplit("I think, therefore I am",",") 

Compared to strsplit, the tstrsplit function performs a transpose operation on the split vector. This is helpful when splitting strings and updating say, a column in a DataFrame:

tstrsplit("I think, therefore I am",",") 

 The difference can be easily observed herein:

# Create a simple data frame 
df <- data.frame(a=c(1,2)) 
 
# strsplit creates a vector 
df$s <- strsplit("I think, therefore I am",",") 
df 
 
# a                        s 
# 1 1 I think,  therefore I am 
# 2 2 I think,  therefore I am 
 
 
# tstrsplit creates a transpose of the vector, t 
df$s <- tstrsplit("I think, therefore I am",",") 
df 
 
# a               s 
# 1 1         I think 
# 2 2  therefore I am