R Quotes In String
3.3 Generic printing
The workhorse printing function in R is print(). As itsnames indicates, this function prints its argument on the R console:
This book aims to provide a panoramic perspective of the wide array of string manipulations that you can perform with R. If you are new to R, or lack experience working with character data, this book will help you get started with the basics of handling strings. Likewise, if you are already familiar with R, you will find material that shows you how to do more advanced string and text. Typically, we use quote to capture names. You can also convert a string to a name with as.name. However, this is most useful only when your function receives strings as input. Otherwise it involves more typing than using quote. (You can use is.name to test if an object is a name.).
To be more precise, print() is a generic function, which means that youshould use this function when creating printing methods for programmed classes.
As you can see from the previous example, print() displays text inquoted form by default. If you want to print character strings with no quotesyou can set the argument quote = FALSE
3.3.1 When to use print()?
When you type the name of an obbject in the R console, R calls the correspondingprint method associated to the class of the object. If the object is a'data.frame', then R will dispatch the method print.data.frame and displaythe output on screen accordingly.
Most of the times you don’t really need to invoke print(). Usually, simplytyping the name of the object will suffice. So when do you actually callprint()? You use print() when your code is inside an R expression(i.e. code inside curly braces { }) and you want to see the results of oneor more computational steps. Typical examples that require an explicit call toprint() is when you are interested in looking at some value within a loop,or a conditional structure.
R Quotes In String
Consider the following dummy for loop. It iterates five times, eachtime adding 1 to the value of the iterator i:
R Quotes In String Quartets
The above code works and R executes the additions, but nothing is displayed onthe console. This is because the command i + 1 forms part of an R expression,that is, it is within the braces { }.To be able to see the actual computations you should call print() like so: