In this tutorial, I will explain how to extract n leading or trailing characters from a string in R. I will structure the article as follows: Show
Let’s move directly to the R syntax… Create Example Character StringIn the examples of this R tutorial, I will use the following character string: x <- "this is an example" # Create example character string Our example string contains the sentence “this is an example”. Now let’s see how we can get the first and last n characters of this example string… Example 1: Extract First n Characters from String in RIn the first example, you will learn how to get the first n characters of a string. For this task, we can use the substr function: substr(x, 1, 3) # Extract first three characters # "thi" As you can see based on the previous R code, the substr function returned thi to the RStudio console (i.e. the first three characters). In order to extract the first n characters with the substr command, we needed to specify three values within the function:
Looks good! So what if we want to get the last n characters of our example data? That’s what you will learn in the next two examples… Example 2: Extract Last n Characters from String in Base RIn the second example, I will also use the substr function (as in Example 1). However, this time the code is getting a bit more complex: n_last <- 3 # Specify number of characters to extract substr(x, nchar(x) - n_last + 1, nchar(x)) # Extract last three characters # "ple" As you can see based on the previous output, we have extracted the characters ple, i.e. the last three characters of our example string. In order to do that, we had to specify three inputs for the substr function again:
Works fine, but admittedly this code is more complicated as in Example 1. For that reason, I’m going to show you an easier solution for extracting the last n characters of a string in the next example… Example 3: Extract Last n Characters from String in R with the stringr PackageThe stringr R package provides an easy way for getting the last n characters of a string. Let’s install and load the package first: install.packages("stringr") # Install stringr package in R library("stringr") # Load stringr package Now we can use the str_sub function of the stringr package as follows: str_sub(x, - 3, - 1) # Extract last characters with str_sub # "ple" The same output as before with the substr function (i.e. ple), but this time with a much simpler R syntax. To get this output, we had to specify three inputs for the str_sub function:
For further explanations, you might also have a look at the R documentation of the str_sub command: Figure 1: str_sub Function Help Documentation. Much easier than the substr base R solution, if you ask me! Tutorial Video & Further Resources on the Handling of StringsI have also published a video tutorial on this topic, so if you are still struggling with the code, watch the following video on my YouTube channel: Dealing with strings in the R programming language can be tricky. If you want to improve your knowledge about the handling of strings in R, I can recommend the following video of the Tutorials Point YouTube channel. The speaker gives general advice how to deal with strings in R. Furthermore, you could also have a look at the following articles and overviews of this website:
In this tutorial, you should have learned how to extract the first and the last n characters of a string in R. However, if you have further questions, don’t hesitate to let me know in the comments below! How do I select the first 4 columns in pandas?There are three basic methods you can use to select multiple columns of a pandas DataFrame:. Method 1: Select Columns by Index df_new = df. iloc[:, [0,1,3]]. Method 2: Select Columns in Index Range df_new = df. iloc[:, 0:3]. Method 3: Select Columns by Name df_new = df[['col1', 'col2']]. How do you print the first three characters of a string in Python?# Get first character of string i.e. char at index position 0. first_char = sample_str[0] ... . # Get First 3 character of a string in python. first_chars = sample_str[0:3] ... . # Get First 4 character of a string in python. first_chars = sample_str[0:4] ... . sample_str = "Hello World !!" # Accessing out of range element causes error.. How do you get the first element of a string in Python?Use the indexing notation string[index] with index as 0 to get the first character of a string.
What is first () in pandas?Pandas DataFrame first() Method
The first() method returns the first n rows, based on the specified value. The index have to be dates for this method to work as expected.
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