R Warning Message: NAs Introduced by Coercion (Example)

This article explains how to debug the warning message “NAs introduced by coercion” in the R programming language.

The content of the post is structured as follows:

1) Creation of Example Data

2) Example 1: Reproduce the Warning Message: NAs Introduced by Coercion

3) Example 2: Modify Data to Avoid Warning Message Using gsub() Function

4) Example 3: Suppress Warning Message Using suppressWarnings() Function

5) Video, Further Resources & Summary

Let’s dive into it…

Creation of Example Data

First, I’ll have to create some example data.

vec <- c("50", "200", "1,000", "10", "1200", "2,100")  # Create example vector
vec                                                    # Print example vector
# [1] "50"    "200"   "1,000" "10"    "1200"  "2,100"

Have a look at the previous RStudio console output. It shows that our example data is a vector of character strings containing six vector elements.

Example 1: Reproduce the Warning Message: NAs Introduced by Coercion

In this example, I’ll show how to replicate the warning message “NAs introduced by coercion” when using the as.numeric function in R. Let’s apply the as.numeric function to our example vector:

as.numeric(vec)                                        # Applying as.numeric function
# [1]   50  200   NA   10 1200   NA
# Warning message:
# NAs introduced by coercion

As you can see, the warning message “NAs introduced by coercion” is returned and some output values are NA (i.e. missing data or not available data).

The reason for this is that some of the character strings are not properly formatted numbers and hence cannot be converted to the numeric class.

The next example shows how to solve this problem in R.

Example 2: Modify Data to Avoid Warning Message Using gsub() Function

In Example 2, I’ll illustrate how to handle the as.numeric() warning message “NAs introduced by coercion”.

As explained before, some of our input values are not formatted properly, because they contain commas (i.e. ,) between the numbers. We can remove these commas by using the gsub function:

vec_new <- gsub(",", "", vec)                          # Applying gsub function
vec_new                                                # Print updated example vector
# [1] "50"   "200"  "1000" "10"   "1200" "2100"

Have a look at the previous output of the RStudio console. It shows that our updated vector does not contain commas anymore.

Now, let’s apply the as numeric function again:

as.numeric(vec_new)                                    # Applying as.numeric function
# [1]   50  200 1000   10 1200 2100

As you can see, we did not only avoid the warning message, we also created an output vector without any NA values.

Example 3: Suppress Warning Message Using suppressWarnings() Function

Sometimes you might not want to convert non-number values to numeric. In this case, you can simply ignore the warning message “NAs introduced by coercion” by wrapping the suppressWarnings function around the as.numeric function:

suppressWarnings(as.numeric(vec))                      # Applying suppressWarnings function
# [1]   50  200   NA   10 1200   NA

The output is the same as in Example 1, but this time without printing the warning message to the RStudio console.

Video, Further Resources & Summary

Do you want to know more about warnings and errors in R? Then I can recommend watching the following video of my YouTube channel. In the video, I’m explaining the R programming codes of this tutorial in a live programming session.

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In addition, you might have a look at the related articles of my homepage. You can find some tutorials about warning and error messages below.

Summary: In this post, I explained how to get rid of the warning “NAs introduced by coercion” when converting a character or factor variable to numeric in the R programming language.

In case you have further questions, don’t hesitate to let me know in the comments section. Furthermore, please subscribe to my email newsletter in order to get updates on new tutorials.

36 Comments. Leave new

Ali H
April 15, 2021 7:30 pm

Hi Joachim, thanks for this tutorial and your help in advance!
I am having the error NAs introduced by coercion. In my case however I am trying to reformat the string characters (e.g. green, blue, red) from two specific columns so that the characters (e.g. green) is represented by a numeric number (e.g. 1) I’ve been trying a long while now so that I can use the data as part of a neural network but cannot get past this error. Can you help me with this?

Reply
- Joachim
  April 16, 2021 6:36 am
  Hi Ali,
  
  Thank you for the very kind words and your interesting question. A simple solution might be the following:
  x <- c("green", "red", "green", "blue", "blue", "yellow") x_num <- as.numeric(as.factor(x_fac)) x_num [1] 2 3 2 1 1 4
  x <- c("green", "red", "green", "blue", "blue", "yellow") x_num <- as.numeric(as.factor(x_fac)) x_num [1] 2 3 2 1 1 4
  Note that the numeric output would be based on the alphabetic order of the input vector.
  
  I hope that helps!
  
  Joachim
  Reply
Angi
June 24, 2021 9:21 pm

Hi Joachim,
Your blog has been a godsend! and I’m hoping you can solve this: My character vector (“1”, “2”, “3”) has zero-width non printing spaces (‘\u200b’)in it (I rvested some Covid data online). I managed to remove most of them with str_remove and then convert the characters into numbers. But it still spits out this message “NAs introduced by coercion” and I don’t know what to look for! Would appreciate any guidance. Thank you!

Reply
- Joachim
  June 25, 2021 8:32 am
  Hey Angi,
  
  Thanks a lot for this amazing feedback! 🙂
  
  You could use the following code to identify all data cells that are converted to NA:
  x <- c("1", "2", "a", "3", "b") x_test <- as.numeric(x) x[is.na(x_test)] # [1] "a" "b"
  x <- c("1", "2", "a", "3", "b") x_test <- as.numeric(x) x[is.na(x_test)] # [1] "a" "b"
  I hope that helps!
  
  Joachim
  Reply
  - Angi
    June 26, 2021 7:47 pm
    
    Thanks Joachim. The problem was figuring 1) the “invisible” mystery character that was creating the issue. Since I tend to glimpse() at my data rather than head() it, I couldn’t see anything wrong. Till I used head(). 2) The culprit was a zero-width non-printing space that was seemingly immune to str_remove() in its original form “”. But 48 hours later, a good learning experience.
    
    Reply
    - Joachim
      June 28, 2021 6:31 am
      
      Glad you found a solution Angi, and thanks for sharing it here! I’m sure others will have similar problems and will benefit from your explanation. 🙂
      
      Regards
      
      Joachim
      
      Reply
Ugi
November 8, 2021 5:14 pm

Hi Joachim, thank you but this function gsub(“,”, “”, vec) remove all the comma’s. But what if we had values with comma for example when our vector is like vec <- c("50,1", "200,3", "1,000,5", "10,3", "1200", "2,100")

Reply
- Joachim
  November 9, 2021 6:55 am
  Hey Ugi,
  
  In this case, you would have to replace the comma by a point. Have a look at the example code below:
  vec <- c("50,1", "200,3", "1000,5", "10,3", "1200", "2,100") vec_new <- as.numeric(gsub(",", ".", vec)) vec_new # [1] 50.1 200.3 1000.5 10.3 1200.0 2.1
  vec <- c("50,1", "200,3", "1000,5", "10,3", "1200", "2,100") vec_new <- as.numeric(gsub(",", ".", vec)) vec_new # [1] 50.1 200.3 1000.5 10.3 1200.0 2.1
  Please note that your example vector contained the value “1,000,5” (i.e. two commas). This does not make sense in case the comma is used as a decimal comma.
  
  I hope that helps!
  
  Joachim
  Reply

Ugi

November 12, 2021 9:55 am

Hi Joachim, thank you very much this does work but i have another problem. I try to change a data frame with several columns where the elements are saved as character elements: It looks like this: BAYER DAIMLER DBANK SIEMENS VONOVIA
[1,] “65,24” “47” “6,809” “89,073” “46,34”
[2,] “65,79” “46,91” “6,839” “89,29” “46,6”
[3,] “66,59” “47,92” “7,079” “90,056” “47,69”

If i use this function as.numeric(gsub(“,”, “.”, vec) it does change the character elements in numerical but i loose the structure of this data frame and get a vector with only one column which looks like this:
[1] 65.24 65.79 66.59 66.22 65.78 64.99

Do you how i can change the character elements into numerical but dont loose the complete structure of the data frame?

Joachim

November 13, 2021 9:47 am

Hey Ugi,

Please have a look at the following example code. I assume this works for your data as well:

data <- data.frame(BAYER = c("65,24", "65,79", "66,59"),
                   DAIMLER = c("47", "46,91", "47,92"))
data # Example data
#   BAYER DAIMLER
# 1 65,24      47
# 2 65,79   46,91
# 3 66,59   47,92
 
data_num <- as.data.frame(apply(data, 2, function(x) as.numeric(gsub(",", ".", x))))
data_num # Modified data
#   BAYER DAIMLER
# 1 65.24   47.00
# 2 65.79   46.91
# 3 66.59   47.92

Regards,
Joachim

Ira St
November 29, 2021 4:33 am

My code for ANOVA also showed this message, for each row of the dataframe:
There were 22 warnings (use warnings() to see them)
>
> warnings()
Warning messages:
1: In FUN(newX[, i], …) : NAs introduced by coercion
2: In FUN(newX[, i], …) : NAs introduced by coercion
3: In FUN(newX[, i], …) : NAs introduced by coercion
4: In FUN(newX[, i], …) : NAs introduced by coercion
5: In FUN(newX[, i], …) : NAs introduced by coercion
6: In FUN(newX[, i], …) : NAs introduced by coercion
7: In FUN(newX[, i], …) : NAs introduced by coercion
8: In FUN(newX[, i], …) : NAs introduced by coercion
9: In FUN(newX[, i], …) : NAs introduced by coercion
10: In FUN(newX[, i], …) : NAs introduced by coercion
11: In FUN(newX[, i], …) : NAs introduced by coercion
12: In FUN(newX[, i], …) : NAs introduced by coercion
13: In FUN(newX[, i], …) : NAs introduced by coercion
14: In FUN(newX[, i], …) : NAs introduced by coercion
15: In FUN(newX[, i], …) : NAs introduced by coercion
16: In FUN(newX[, i], …) : NAs introduced by coercion
17: In FUN(newX[, i], …) : NAs introduced by coercion
18: In FUN(newX[, i], …) : NAs introduced by coercion
19: In FUN(newX[, i], …) : NAs introduced by coercion
20: In FUN(newX[, i], …) : NAs introduced by coercion
21: In FUN(newX[, i], …) : NAs introduced by coercion
22: In FUN(newX[, i], …) : NAs introduced by coercion

The code is:

#assigning X vector #obtain classifications for samples

Control <-datout.new$clas == "Control"
TB <-datout.new$clas == "TB"
Sarcoidosis <-datout.new$clas == "Sarcoidosis"

#1-factor ANOVA with 3 levels
aov.all.genes <- function(x,s1,s2,s3) {
x1 <- as.numeric(x[s1])
x2 <- as.numeric(x[s2])
x3 <- as.numeric(x[s3])
fac <- c(rep("A",length(x1)), rep("B",length(x2)), rep("C",length(x3)))
a.dat <- data.frame(as.factor(fac),c(x1,x2,x3))
names(a.dat) <- c("factor","express")
p.out <- summary(aov(express~factor, a.dat))[[1]][1,5]
return(p.out) }

aov.run <- apply(datout.new,1, aov.all.genes,s1=Control,s2=Sarcoidosis,s3=TB)

Reply
- Joachim
  November 29, 2021 7:06 am
  
  Hey Ira,
  
  It seems like your variables Control, Sarcoidosis, and TB are not formatted properly. Could you illustrate how these variables look like?
  
  Regards,
  Joachim
  
  Reply
Pinky
March 29, 2022 1:05 pm

Hi Joachim, ur blog is amazing!
I’m hoping that you can solve this: My character factor W is in the data set of XYZ.
W has value such as “1”, “2”, “3”, “101-200”, “101-200″,”101-200”,NA, NA. I have tried: as.integer(as.factor(XYZ$W)) and also
as.integer(as.factor(W))

However, when I determine if I have changed the W character to integer, so I check it with both:
as.integer(W) –> TRUE
as.integer(XYZ$W) –> FALSE

But, when i type in: str(XYZ), it shows the W is still in character form.

Could you help me look over how to change the factor to integer?
I would really appreciate if you can help me with this. Thank you!

Reply
- Joachim
  March 29, 2022 3:54 pm
  Hey Pinky,
  
  First of all, thanks a lot for the very kind words! Glad you like my tutorials! 🙂
  
  Regarding your question, please have a look at the code below. First we have to create some example data:
  x <- c("1", "2", "3", "101-200", "101-200", "101-200", NA, NA) x # [1] "1" "2" "3" "101-200" "101-200" "101-200" NA NA
  x <- c("1", "2", "3", "101-200", "101-200", "101-200", NA, NA) x # [1] "1" "2" "3" "101-200" "101-200" "101-200" NA NA
  Next, we can convert these data to numeric using the as.numeric function:
  x_num1 <- as.numeric(x) x_num1 # [1] 1 2 3 NA NA NA NA NA
  x_num1 <- as.numeric(x) x_num1 # [1] 1 2 3 NA NA NA NA NA
  Note that the previous code has replaced “101-200” by NA, since this character string cannot be represented as a numeric (or integer value).
  
  If you want to avoid this, you may insert an average value for these strings:
  x_num2 <- x x_num2[x_num2 == "101-200"] <- "150" x_num2 <- as.numeric(x_num2) x_num2 # [1] 1 2 3 150 150 150 NA NA
  x_num2 <- x x_num2[x_num2 == "101-200"] <- "150" x_num2 <- as.numeric(x_num2) x_num2 # [1] 1 2 3 150 150 150 NA NA
  In the previous code, I have replaced “101-200” by 150.
  
  I hope that helps!
  
  Joachim
  Reply
Pitch
April 3, 2022 5:08 am

Hi Joachim, first I’ll like to thank you so much for the help and amazing work you’re doing right here. I’ll need you to please help convert a column from my dataset containing time duration in format “hms” to numeric. Here’s a view of the column

glimpse(Annual_Trips$ride_length)
‘hms’ num [1:5595063] 00:10:25 00:04:04 00:01:20 00:11:42 …
– attr(*, “units”)= chr “secs”

Tried applying the gsub function and taught of replacing the ‘,’ with the ‘:’ but still got a column full of NAs.
Thanks in advance

Reply
- Joachim
  April 4, 2022 6:30 am
  
  Hey Pitch,
  
  Thank you so much for the great feedback, glad you like my tutorials! 🙂
  
  Also, thanks for the interesting question. It has inspired me top create a new tutorial on how to convert hours, minutes, and seconds to a numeric seconds object.
  
  Please have a look here.
  
  I hope that helps!
  
  Joachim
  
  Reply
  - Pitch
    April 4, 2022 8:21 pm
    
    Hi Joachim thanks for this tutorial.
    Followed the steps and it worked perfectly. Thank you very much
    
    Reply
    - Joachim
      April 5, 2022 6:01 am
      
      You are very welcome, glad it worked! 🙂
      
      Reply
Danijela
June 28, 2022 8:20 pm

Hi Joachim,
I’m new here so I will be very happy if you can help me with my data.

I try to convert my variable “Year”, that is a character to numeric. This is my complete code:

FD = read_csv(“FAO_Fishingdata_2021.csv”)

FD2 %
pivot_longer(cols = 4:72, names_to = “Year”, values_to = “Catch”) %>%
mutate(Year = as.numeric(“Year”))

But as a result I get a collum “Year” with all NAs…
What am I doing wrong?

Thank you!

Reply
- Joachim
  June 29, 2022 6:01 am
  
  Hey Danijela,
  
  Could you please share some example values that are contained in the Year column?
  
  Regards,
  Joachim
  
  Reply

Annemarie

July 7, 2022 7:24 am

Hi Joachim,
Thank you so much for your tutorials! Hope you can help me with my problem!
I have pH values from some samples – but a lot of NA’s as well. I would like to tell R that it is numeric values, but when I use the as.numeric function I get the warning: nas introduced by coercion. I loos all the numbers as it convert it to NA’s

[1] NA NA NA 6.51 6.18 NA 6.43 6.73 NA 6.56 6.02 NA NA 7.31 NA 6.56 6.17 NA 7.31 6.78
[21] NA 5.25 5.44 NA NA NA

d$kat_urinph <- as.numeric(d$kat_urinph)
Warning message:
NAs introduced by coercion

Joachim

July 8, 2022 7:13 pm

Hey Annemarie,

Thank you very much for the kind feedback, glad you like my tutorials!

Regarding your question, I can convert the values you have posted above to numeric without having any problems. See the example code below:

x <- c(NA, NA, NA, "6.51", "6.18", NA, "6.43", "6.73", NA, "6.56", "6.02", NA, NA, "7.31", NA, "6.56", "6.17", NA, "7.31", "6.78", NA, "5.25", "5.44", NA, NA, NA)
x
#  [1] NA     NA     NA     "6.51" "6.18" NA     "6.43" "6.73" NA     "6.56" "6.02" NA     NA     "7.31" NA     "6.56" "6.17" NA     "7.31" "6.78" NA     "5.25" "5.44" NA     NA     NA    
 
x_num <- as.numeric(x)
x_num
#  [1]   NA   NA   NA 6.51 6.18   NA 6.43 6.73   NA 6.56 6.02   NA   NA 7.31   NA 6.56 6.17   NA 7.31 6.78   NA 5.25 5.44   NA   NA   NA

Are there maybe any other values in your data that are converted differently?

Regards,
Joachim

Erika

July 11, 2022 10:41 am

Hi Joachim,

thank you for your work and all of your tutorials, they always help a lot.
I am currently experiencing the same problem with the NA introduced by coercion in my dataset.
I already figured out that there must be a problem with the format of the negative values in my dataset, however, I haven’t found a solution yet to solve this issue.
This is a little example of the values:
EBIT_dax$`2020`
[1] “739000.00” “10603000.00” “-1055000.00” “5481000.00” “-15692000.00” “-772500.00”

And this is how I tried to solve the issue (which didn’t end up working):
EBIT_dax[ ,9] <-apply(EBIT_dax,2, function(x){as.numeric(as.character(gsub("-", "\U2212",x)))})
The then new output shows all negative values as NA.

Do you have a tip for me on how to solve this?

Thank you and regards
Erika

Joachim

July 12, 2022 2:12 pm

Hi Erika,

Thank you for the kind comment, glad you find the tutorials on Statistics Globe useful!

Regarding your question, you may convert all the columns in your data set to numeric as shown in the following example:

EBIT_dax <- data.frame(x1 = c("739000.00", "10603000.00", "-1055000.00", "5481000.00", "-15692000.00", "-772500.00"),
                       x2 = c("739000.00", "10603000.00", "-1055000.00", "5481000.00", "-15692000.00", "-772500.00"))
 
EBIT_dax_num <- apply(EBIT_dax, 2,
                      function(x) as.numeric(as.character(x)))
EBIT_dax_num
#             x1        x2
# [1,]    739000    739000
# [2,]  10603000  10603000
# [3,]  -1055000  -1055000
# [4,]   5481000   5481000
# [5,] -15692000 -15692000
# [6,]   -772500   -772500

You can find more information on this method here.

Regards,
Joachim

Helena
August 8, 2022 9:27 pm

Thank you very much for this tutorial! My script finally is running properly!

Reply
- Joachim
  August 9, 2022 6:37 am
  
  Hey Helena,
  
  Thank you very much for the kind comment, glad it helped!
  
  Regards,
  Joachim
  
  Reply
Herme
September 7, 2022 4:11 pm

Hey Joachim, thank you very much for this tutorial; it helped me a lot to understand how these functions work.
I have a similar problem: I am trying to do some spatial analysis with a csv file that has been exported by ArcGIS and contains X and Y coordinates. However when I try this

“`
pottery <- read.csv (file="pots.csv", header=TRUE)
coordinates(pottery) <- ~XCoord+YCoord
“`

I get this error: Error in .local(obj, …) : cannot derive coordinates from non-numeric matrix

When I tried the `as.numeric()` I also got NAs introduced by coercion

My question is: Will r be able to distinguise the variables and columns if I remove the commas (,) from my coordinate columns?

I am also including the dataframe:

“`
str(pottery)
'data.frame': 601 obs. of 14 variables:
$ XCoord : chr "1277.10140000" "1281.93990000" "1309.94460000" "1301.58720000" …
$ YCoord : chr "-915.96560000" "-930.18790000" "-939.57170000" "-931.36080000" …
$ pottery.POINT_X: chr "1277.101400" "1281.939900" "1309.944600" "1301.587200" …
$ pottery.POINT_Y: chr "-915.965600" "-930.187900" "-939.571700" "-931.360800" …
$ Object : chr "P73" "P474" "P587" "P629" …
$ Shape : chr "Amphora" "Jug" "Pithoid" "Pithos" …
$ Use : chr "Storing" "Pouring" "Storing" "Storing" …
$ Height : chr "86.8" "15" "NULL" "68.5" …
$ Fabric : chr "M" "S" "M" "S" …
$ Decoration : chr "Yes" "Yes" "Yes" "Yes" …
$ Pattern : chr "Running Drops" "NULL" "Bands" "Running Drops" …
$ Style : chr "Dark on light" "Painted" "Dark on light" "Dark on light" …
$ Floor : chr "No" "No" "No" "No" …
$ Fill : chr "No" "No" "No" "No" …
“`

Reply
- Joachim
  September 8, 2022 6:40 am
  Hi Herme,
  
  Thank you for the kind comment, glad you find the tutorial helpful!
  
  I do not have experience with your functions. However, when I try to convert your data to numeric, I do not get this warning:
  x <- c("1277.10140000", "1281.93990000", "1309.94460000") as.numeric(x)
  x <- c("1277.10140000", "1281.93990000", "1309.94460000") as.numeric(x)
  Maybe it makes sense to identify the non-numeric values in your data first? Have a look here.
  
  Regards,
  Joachim
  Reply
Harsh
October 2, 2022 5:21 am

ID age fl lake era
1 1 14 459 Harrison 1977-80
2 2 12 449 Harrison 1977-80
3 3 10 471 Harrison 1977-80
59 59 7 245 Harrison 1997-01
60 60 7 279 Harrison 1997-01
61 61 5 245 Harrison 1997-01

Que : Convert the tmp era values to numeric values.

tmp$era <- as.numeric(tmp$era)
tmp$era

This shows error as it gives NA as the result.

I've tried this :
tmp$era <- tmp
tmp$era[tmp$era == "1977-80"] <- "1978"
tmp$era <- as.numeric(tmp$era1)
tmp$era1

But this gives error :
Error in `$<-.data.frame`(`*tmp*`, era, value = numeric(0)) : replacement has 0 rows, data has 6

Can you please help with this !!

Reply
- Joachim
  October 5, 2022 8:46 am
  
  Hi Harsh,
  
  Your column era is not a number, so it cannot be converted to numeric without any preprocessing. Could you please tell me what the desired output for this column should look like?
  
  Regards,
  Joachim
  
  Reply
Chimee
November 24, 2022 1:27 am

I want to convert the test result from “-” and “+” to 0 and 1. And there, empty cell, how can i solve it?

Reply
- Joachim
  November 24, 2022 7:59 am
  
  Hey Chimee,
  
  Are the empty cells formatted as blank characters (i.e. “”)? In this case, you may convert them to NA as explained here.
  
  Regards,
  Joachim
  
  Reply
Jordan Reitemeyer
January 11, 2023 2:45 pm

Hello Jochaim,
thank you for your work and all of your tutorials, they always help a lot.
I have to convert the column “EU27” (in character) from Dataframe (“Data”) into numeric.
Somehow it won’t work because of NAs: Warning: NAs introduced by coercion.
Regards,
Jordan

Reply
- Cansu (Statistics Globe)
  January 11, 2023 5:45 pm
  
  Hello Jordan,
  
  This error is received due to the wrong formatting of the inputs in character type. The tutorial shows only one possible misformatting. But in the comment section, many other misformattings have already been discussed. You may want to look at them if you haven’t done it yet. If you still struggle maybe you can provide a screenshot of your data for me to check it.
  
  Regards,
  Cansu
  
  Reply
Stefan
January 13, 2023 8:08 am

Hi Joachim,
Thanks for the explanation and everyone for the helpful discussion!
I am getting the “NAs introduced by coercion” warning as well in my pipeline. I noticed that you always get it, even if you explicitly assign NA values (just like in the first example you give).
One would conclude that R does not encourage you to (willingly) create NA in data (even when there is actually missing data).
Is there another way to do this that IS encouraged (i.e. that is considered good coding style and doesn’t give any warnings)?
I don’t think it’s a good idea to bloat up your code with suppressWarnings() left and right X-D

Reply
- Cansu (Statistics Globe)
  January 13, 2023 10:32 am
  
  Hello Stefan,
  
  To be honest, I don’t know about the alternatives. But I found this StackOverflow thread which might be useful to check out.
  
  Regards,
  Cansu
  
  Reply