#Input some text into a vector
StringVector<-c("Good","Nice","Smart","Cool")
#This function will return the position of the string we are looking for in the vector, if it exist
grep("Cool",StringVector)
#if it doesnot exist the function will return
grep("BAD",StringVector)

#grepl works in the same way as grep
#but instead of returning the position, it retuns a logical result for each vector position
grepl("Cool",StringVector)

#Let's see if we can check a if column exists in a dataframe.
#we will use the dataset mtcars
head(mtcars)
#for example, we want to have a list of all the cars that start with the letter "M"

mtcars[grep("M",row.names(mtcars)),]

#substitute a string with an other one:
gsub("Cool","Not",StringVector)
#for a data frame:
d<-mtcars
row.names(d)<-gsub("Mazda","MZ",row.names(d))

#Let's replace white spaces with " _ "
#here we will need the stringr library
library(stringr)
row.names(d)<-str_replace(row.names(d)," ","_")