R error: ‘\u’ used without hex digits in character string starting “”c:\u”

Getting error messages is an inevitable part of programming. Not only can you make typographical errors from time to time, but they can also result from other problems. Because they are inevitable, you need to learn how to handle error messages as well as what causes them to come up. A common source of error messages comes from loading files and this one results from the improper formatting of the file address.

Circumstances of this error message.

(‘\u’ used without hex digits in character string starting “”c:\u”)

This error can occur when using read.csv() function if the file name and location are not formatted properly. Unfortunately, the description in the error message itself does not provide any useful information to the average programmer. The reason this can be confusing is that you would not expect to see hexadecimal digits in the address of a file. An example of this problem can be seen in the following code.

# error source: '\u' used without hex digits in character string starting ""c:\u"
x=read.csv("C:\Users\Bob\Desktop\problem.csv")

At first glance, it does not look like there is anything wrong here, after all, the file address is properly formatted if you are entering it into your computer’s “command prompt.” The problem is that this format is not correct when using it here.

Reason for this error message.

This error message occurs at the first backslash. It is a result of the fact that the backslash serves as an indicator of string literals. String literals are a character or string in quotes with a special meaning. These meanings include the formatting of the text, octal numbers, and hexadecimal number. So when you use a single backslash followed by a letter, it is looking for that special meaning. Because the letter “U” does not have a special meaning, it looks to “x” which indicates a hexadecimal number. Because of this, you cannot use backslashes in this manner and the program to produce this error message if you try.

How to fix this error message.

Fixing this problem is actually quite easy. Even better you do have just have one solution but three. All three of these methods use a different way of avoiding this backslash problem.

# solution 1: '\u' used without hex digits in character string starting ""c:\u"
x = read.csv("C:\\Users\\Bob\\Desktop\\problem.csv")

The first way is to simply add a second backslash. This is because “\\” has the special meaning of a single backslash.

# solution 2: '\u' used without hex digits in character string starting ""c:\u" 
x = read.csv("C:/Users/Bob/Desktop/problem.csv")

The second way is to use a forward-slash. This approach gets around the problem by eliminating the backslash all together.

# solution 3: '\u' used without hex digits in character string starting ""c:\u"
x = read.csv(file = "C:\Users\Bob\Desktop\problem.csv")

The third way is to equate the string to the file variable in the read.csv() function. This approach keeps the original format while eliminating special meanings.

This is an easy error to make because the standard file address system does not work as expected. However, it is an easy one to correct and avoid once you become aware of it. You can use any of these three solutions to avoid this error message, so feel free to try them all.

For error: ‘\u’ used without hex digits in character string starting “”c:\u”