Create a Scatterplot in R with ggplot

Learn how to build a custom R function that uses ggplot and base R to generate scatterplots with user-defined data inputs.
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This video is based on the question https://stackoverflow.com/q/70787550/ asked by the user 'JohnJ' ( https://stackoverflow.com/u/17731737/ ) and on the answer https://stackoverflow.com/a/70787805/ provided by the user 'Grzegorz Sapijaszko' ( https://stackoverflow.com/u/17486894/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Creating a Scatterplot in R with ggplot: A Step-by-Step Guide

When working with R, visualizing data is an essential part of the analysis process. One common way to visualize relationships between two numeric variables is through scatterplots. In this guide, we’ll learn how to create a custom R function that accepts a DataFrame and two specified columns to generate scatterplots using both ggplot2 and base R's plot function.

The Problem

You have a DataFrame containing several columns of numeric data, and you want to create a scatterplot depicting the relationship between two specific columns. You also want to ensure that your function validates the input columns, providing informative error messages when necessary.

To illustrate this, we’ll use a sample DataFrame:

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The Solution

Step 1: Define the Function

We will create a function called test that takes three parameters:

Data: the DataFrame

ing1: the name of the first column

ing2: the name of the second column

Here's how to define the function:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Validate Inputs

Before creating the scatterplots, we need to check whether the provided column names ing1 and ing2 exist in the DataFrame (i.e., they are valid inputs). The condition ing1 %in% names(Data) checks if ing1 is one of the column names in the DataFrame.

If either of the inputs is invalid, we’ll print an error message:

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Step 3: Generate Scatterplots

Once we confirm that the inputs are valid, we can create scatterplots using ggplot2:

[[See Video to Reveal this Text or Code Snippet]]

The aes_string function allows us to use character strings for column names.

Step 4: Complete Function Implementation

Here's the complete implementation of the function that creates both a scatterplot using ggplot and base R’s plot.

[[See Video to Reveal this Text or Code Snippet]]

Step 5: Testing the Function

Now, you can test the function with the sample DataFrame and different column names:

[[See Video to Reveal this Text or Code Snippet]]

You can also test invalid inputs to see if the error handling works correctly:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the steps outlined in this guide, you can create a functional R script that generates scatterplots using both ggplot2 and base R's plot. This approach not only provides a useful visualization tool but also reinforces the importance of validating your inputs. Happy plotting!