How To Fix The R Error: discrete value supplied to continuous scale

Hey there, fellow R enthusiasts! Have you ever tried to create a plot in R, only to be met with a cryptic error message that says “Discrete value supplied to continuous scale”? Don’t worry, you’re not alone! This error message can be frustrating and confusing, but fear not – we’re here to help you understand what it means and how to fix it. In this article, we’ll explore the common causes of the “Discrete value supplied to continuous scale” error message and provide some tips and tricks for resolving it.

When Does This Error Happen?

The “discrete value supplied to continuous scale” message occurs when using the ggplot() function along with the scale__continuous()scale function to specify a specific scale for a graph.

# this error is related to the ggplot2 library, so we need to load it (if you haven't already)
install.packages("ggplot2")
library("ggplot2")

# r error discrete value supplied to continuous scale
> a = data.frame(x = 1:10, y = c("cat", "dog", "bat", "cow", "rat"))
> ggplot(a, aes(x, y)) + geom_point()

In this example of the basic usage of ggplot(), the scale function is not used. However, it does produce a successful graph of the data frame. Getting this message requires including the scale function and doing so incorrectly. That turns out to be the key to fixing the continuous variable problem and that is using the scale function correctly.

What Caused The Error?

The “discrete value supplied to continuous scale” message is caused by erroneous use of the scale function along with ggplot().

# discrete value supplied to continuous scale r error
> a = data.frame(x = 1:10, y = c("cat", "dog", "bat", "cow", "rat"))
> ggplot(a, aes(x, y)) + geom_point() + scale_y_continuous(limits = c(0, 15))
Error: Discrete value supplied to continuous scale

The mistake in this example that leads to the error message is trying to create a continuous scale for the “y” axis. The problem is that the “y” vector is a discrete variable consisting of words, i.e. a character vector or categorical variable, not a numeric vector, which would create continuous data. This means that you are trying to create a continuous value for a discrete value axis. It does not work resulting in our message.

How to Fix This Error – discrete value supplied to continuous scale

The “discrete value supplied to continuous scale” message can be fixed but making sure that at least one of the position scales in the data frame is a continuous value rather than a discrete scale and applying the scale function to that character vector to make it a numeric vector.

# discrete value supplied to continuous scale solution
> a = data.frame(x = 1:10, y = c("cat", "dog", "bat", "cow", "rat"))
> ggplot(a, aes(x, y)) + geom_point() + scale_x_continuous(limits = c(0, 15))

As you can see from this example using “x” instead of “y” in the scale function fixes the problem by supplying a numeric value list instead of characters. This factor makes all the difference.

# discrete value continuous scale r solution
> a = data.frame(x = 1:10, y = c(1:5))
> ggplot(a, aes(x, y)) + geom_point() + scale_y_continuous(limits = c(0, 7))

The other option as seen above is to turn “y” into a numeric list as illustrated above. The one problem with this solution is that the dataset graph, scatter plot, box plot, or bar chart is losing some of its meaning. This is because the model no longer has the categorical variable labels that it previously did.

A Deeper Look at Potential Causes of the Error

The “Discrete value supplied to continuous scale” error message is a common issue that can occur when creating plots in R. This error message indicates that there is a mismatch between the data type or scale type of a variable and the plotting function used to create the plot. There are several potential causes of this error message, including using a continuous scale when the data is discrete, using the wrong data type for a variable, and inconsistent data formatting. By understanding these potential causes, you can more easily diagnose and resolve the “Discrete value supplied to continuous scale” error message in R.

Here are some potential causes of the “Discrete value supplied to continuous scale” error message in R:

Using a continuous scale when the data is discrete:
- If the data is categorical or discrete, such as a factor or character variable, it should be plotted using a discrete scale, such as a factor or date scale. Using a continuous scale, such as a numeric or date-time scale, can result in the “Discrete value supplied to continuous scale” error message.
Using the wrong data type for a variable:
- Simple enough – if there’s a mismatch between the data type and the scale, you’ll get an error message.
Mismatched data types between variables:
- Similar to error #2 – if you’re trying to plot different variables in a multi-variable plot on the same scale, you’ll get an error.
Inconsistent data formatting:
- Formatting variances can throw the code off…
Using the wrong plotting function:
- The function needs to match the data type you’re trying to plot.

By understanding these potential causes of the “Discrete value supplied to continuous scale” error message in R, you can more easily diagnose and resolve the issue when it occurs.

Strategies for Resolving the Error

If you encounter the “Discrete value supplied to continuous scale” error message in R, there are several strategies you can use to resolve the issue. Here are some options to consider:

Converting discrete data to a factor or character type:
- If the data is discrete convert it to the appropriate data type using the as.factor() or as.character() functions, respectively.
Changing the scale type to a discrete scale, such as a factor or date scale:
Using the appropriate plotting function for the data type:

By using these strategies, you can effectively resolve the “Discrete value supplied to continuous scale” error message in R and create accurate and informative plots.

Summation

The “discrete value supplied to continuous scale” error message is more of a minor nuisance than a serious problem. It is simply a matter of using the wrong vector from the data frame. Correcting that one continuous data mistake in your plotting code solves the problem in a simple and easy manner.

R Error: discrete value supplied to continuous scale