How to Solve R Warning: NAs Introduced by Coercion

This warning occurs when you try to convert a vector containing non-numeric values to a numeric vector.

As this is a warning, you do not need to solve anything. However, you can replace non-numeric values or suppress the warning using suppressWarnings().

This tutorial will go through the warning and what to do to stop the warning.

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Example

Consider the following example where we have a vector of type character. Some of the values have commas between numbers.

vec <- c("10", "1,250", "34", "4,500", "20")
class(vec)
vec

[1] "character"
[1] "10"    "1,250" "34"    "4,500" "20"   

Let’s attempt to convert the character vector to a numeric vector using as.numeric().

vec_new <- as.numeric(vec)
vec_new

Let’s run the code to see the result:

Warning message:
NAs introduced by coercion 

[1] 10 NA 34 NA 20

The warning occurs because R could not convert the two values “1,250” and “4,500” to numeric.

Solution #1: Substitute Non-numeric values

If the data is corrupt, we can replace part or all of the values in the vector so R can convert them to numeric. In this case, we can remove the commas in the values using gsub. Let’s look at the revised code.

vec <- gsub(",", "", vec)
vec_new <- as.numeric(vec)
vec_new

Let’s run the code to see the result:

[1]   10 1250   34 4500   20

We successfully converted the character vector to a numeric vector without displaying the warning message,

Solution #2

We may not want to convert the non-numeric values, in which case we can suppress the warning message using the suppressWarnings() built-in function. Let’s look at the revised code:

vec <- c("10", "1,250", "34", "4,500", "20")
suppressWarnings(vec_new <- as.numeric(vec))
vec_new

Let’s run the code to see the result:

[1] 10 NA 34 NA 20

We successfully converted the character vector to a numeric vector without the warning message.

Summary

Congratulations on reading to the end of this tutorial!

For further reading on R related errors, go to the articles: 

• How to Solve R Error in sort.int(x, na.last = na.last, decreasing = decreasing, …) : ‘x’ must be atomic
• How to Solve R Error: attempt to use zero-length variable name

Go to the online courses page on R to learn more about coding in R for data science and machine learning.

Have fun and happy researching!