Why Are Xs Added to Data Frame Variable Names When Using Read.Csv

Why are Xs added to data frame variable names when using read.csv?

read.table and read.csv have a check.names= argument that you can set to FALSE.

For example, try it with this input consisting of just a header:

> read.csv(text = "a,1,b")
[1] a  X1 b 
<0 rows> (or 0-length row.names)

versus

> read.csv(text = "a,1,b", check.names = FALSE)
[1] a 1 b
<0 rows> (or 0-length row.names)

Why am I getting X. in my column names when reading a data frame?

read.csv() is a wrapper around the more general read.table() function. That latter function has argument check.names which is documented as:

check.names: logical.  If ‘TRUE’ then the names of the variables in the
         data frame are checked to ensure that they are syntactically
         valid variable names.  If necessary they are adjusted (by
         ‘make.names’) so that they are, and also to ensure that there
         are no duplicates.

If your header contains labels that are not syntactically valid then make.names() will replace them with a valid name, based upon the invalid name, removing invalid characters and possibly prepending X:

R> make.names("$Foo")
[1] "X.Foo"

This is documented in ?make.names:

Details:

    A syntactically valid name consists of letters, numbers and the
    dot or underline characters and starts with a letter or the dot
    not followed by a number.  Names such as ‘".2way"’ are not valid,
    and neither are the reserved words.

    The definition of a _letter_ depends on the current locale, but
    only ASCII digits are considered to be digits.

    The character ‘"X"’ is prepended if necessary.  All invalid
    characters are translated to ‘"."’.  A missing value is translated
    to ‘"NA"’.  Names which match R keywords have a dot appended to
    them.  Duplicated values are altered by ‘make.unique’.

The behaviour you are seeing is entirely consistent with the documented way read.table() loads in your data. That would suggest that you have syntactically invalid labels in the header row of your CSV file. Note the point above from ?make.names that what is a letter depends on the locale of your system; The CSV file might include a valid character that your text editor will display but if R is not running in the same locale that character may not be valid there, for example?

I would look at the CSV file and identify any non-ASCII characters in the header line; there are possibly non-visible characters (or escape sequences; \t?) in the header row also. A lot may be going on between reading in the file with the non-valid names and displaying it in the console which might be masking the non-valid characters, so don't take the fact that it doesn't show anything wrong without check.names as indicating that the file is OK.

Posting the output of sessionInfo() would also be useful.

Reading CSV in R creates new columns with X

you can try to select the first three columns after reading the file:

df = df[,c(1:3)]

Avoid that space in column name is replaced with period (.) when using read.csv()

If your set check.names=FALSE in read.csv when you read the data in then the names will not be changed and you will not need to edit them before writing the data back out. This of course means that you would need quote the column names (back quotes in some cases) or refer to the columns by location rather than name while editing.

Prevent variable name getting mangled by read.csv/read.table?

This is a BOM (Byte Order Mark) UTF-8 issue.

To prevent this from happening, 2 options:

1. Save your file as UTF-8 without BOM / signature -- or --
2. Use fileEncoding = "UTF-8-BOM" when using read.table or read.csv

Example:

mydata <- read.table(file = "myfile.txt", fileEncoding = "UTF-8-BOM")

R: read.csv adding sub-script X in header

according to @Joshua

read.csv("filename.csv",check.names=FALSE)

R: Why am I getting an extra column titled X.1 in my dataframe after reading my .txt file?

If all other column names are correct, you have probably a trailing \t in the text file. R tries to include it and gives it the generic column name X.1.

You could try and read the file first as 'plain text' and remove the trailing \t and only then use read.csv:

file_connection <- file("Objects_Population - AllCells.txt")
content <- readLines(file_connection )
close(file_connection)

Now we try to get rid of these trailing \t (this might need some testing to fit your needs)

sanitized <- gsub("\\t$", "", content)

And then we read this sanitized string as if it was a file (using the argument text)

df <- read.csv(text=paste0(sanitized, collapse="\n"), sep="\t", skip = 9,header=TRUE, fill = T)

R read.csv Importing Column Names Incorrectly

If you set the argument

check.names = FALSE

in read.csv, then R will not override the names. But these names are not valid in R and they'll have to be handled differently than valid names.

Give column name when read csv file pandas

I'd do it like this:

colnames=['TIME', 'X', 'Y', 'Z'] 
user1 = pd.read_csv('dataset/1.csv', names=colnames, header=None)

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