Find Positions of Dots in Character String in R (3 Examples)


In this R tutorial you’ll learn how to locate all dots (i.e. points) in a character string.

The tutorial contains this:

Let’s dive into it!


Creation of Example Data

The following data will be used as basement for this R tutorial:

my_string <- "aaa.b.cccc.d.e"                     # Create example character string
my_string                                         # Print example character string
# [1] "aaa.b.cccc.d.e"

As you can see based on the previous RStudio console output, our example data is a single character string stored in the data object my_string.


Example 1: Get All Dot Locations in Character String Using gregexpr() & unlist() Functions

Example 1 illustrates how to locate all dots in a character string.

To accomplish this, we can apply the gregexpr and unlist functions to our character string as shown below:

all_dots <- unlist(gregexpr("\.", my_string))    # Get all dot locations
all_dots                                          # Return all dot locations
# [1]  4  6 11 13

The previous output shows the index positions of all dots in our character string.


Example 2: Get Location of First Dot in Character String

In this example, I’ll explain how to extract only the very first dot position in a character string that contains multiple dots.

For this, we can use the data object all_dots that we have created in Example 1 of this tutorial:

first_dot <- all_dots[1]                          # Extract first dot position
first_dot                                         # Print first dot position
# [1] 4

The first dot is located at the fourth character position in our example string.


Example 3: Get Location of Last Dot in Character String

Similar to Example 2, we can use the all_dots data object to find the last dot in a character string.

Consider the following R syntax:

last_dot <- all_dots[length(all_dots)]            # Extract last dot position
last_dot                                          # Print last dot position
# [1] 13

The last dot is at the 13th position of our string.


Video & Further Resources

Have a look at the following video on my YouTube channel. I explain the contents of this tutorial in the video:


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Also, you could have a look at the related tutorials on this website:


To summarize: You have learned in this post how to find all positions of dots in a character string in R programming. Let me know in the comments, if you have further comments or questions.


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