R Warning Message – In Ops.factor : not meaningful for factors (Example)

This article shows how to deal with the warning message “In Ops.factor : not meaningful for factors” in the R programming language.

The article will contain these contents:

Let’s just jump right in.

Creation of Example Data

First, we’ll have to create some example data:

x <- as.factor(c(3, 3, 6, 2, 7, 4, 3, 6, 5))    # Create example data
x                                               # Print example data
# [1] 3 3 6 2 7 4 3 6 5
# Levels: 2 3 4 5 6 7

Have a look at the previous output of the RStudio console. It shows that our example data is a factor vector consisting of different numbers.

Example 1: Reproduce the Warning Message: In Ops.factor(X) : ‘Y’ not meaningful for factors

Example 1 illustrates how to replicate the warning “In Ops.factor : not meaningful for factors”. Let’s assume that we want to do some computations with the numbers contained in our example data:

x^2                                             # False usage of data class 
# [1] NA NA NA NA NA NA NA NA NA
# Warning message:
# In Ops.factor(x, 2) : '^' not meaningful for factors

Then, the warning message “In Ops.factor : not meaningful for factors” is returned.

The reason for this it that our example vector has the factor class. This data type is not suited for numerical computations (such as the square root).

Next, I’ll explain how to solve this problem.

Example 2: Fix the Warning Message: In Ops.factor(X) : ‘Y’ not meaningful for factors

The following R code explains how to fix the issues with the warning message “In Ops.factor : not meaningful for factors”.

As a first step, we have to convert our example data to numeric using the as.numeric and as.character functions:

x_num <- as.numeric(as.character(x))            # Convert factor to numeric
x_num                                           # Print updated data
# [1] 3 3 6 2 7 4 3 6 5

Our updated data object has the numeric class. For that reason, we can now apply any numerical computation without any problems:

x_num^2                                         # Use data for computations
# [1]  9  9 36  4 49 16  9 36 25

Looks good!

Video, Further Resources & Summary

Do you need further information on the R codes of this tutorial? Then you might want to have a look at the following video instruction of the Statistics Globe YouTube channel. In the video instruction, I’m explaining the content of this tutorial in R.

Furthermore, you may read the related tutorials on this website. I have released numerous articles about errors and warning messages already:

• Fixing Warning & Error Messages in R
• The R Programming Language

In this R tutorial you learned how to handle the warning message “In Ops.factor : not meaningful for factors”. Let me know in the comments section, in case you have additional questions.