CODEWITHSUNDEEP
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Aibhilin
Aibhilin

Reputation: 87

Using loop variables

I would like to rename a large number of columns (column headers) to have numerical names rather than combined letter+number names. Because of the way the data is stored in raw format, I cannot just access the correct column numbers by using data[[152]] if I want to interact with a specific column of data (because random questions are filtered completely out of the data due to being long answer comments), but I'd like to be able to access them by data$152. Additionally, approximately half the columns names in my data have loaded with class(data$152) = NULL but class(data[[152]]) = integer (and if I rename the data[[152]] file it appropriately allows me to see class(data$152) as integer).

Thus, is there a way to use the loop iteration number as a column name (something like below)

    for (n in 1:415) {
        names(data)[n] <-"n"    # name nth column after number 'n'
    }

That will reassign all my column headers and ensure that I do not run into question classes resulting in null?

As additional background info, my data is imported from a comma delimited .csv file with the value 99 assigned to answers of NA with the first row being the column names/headers

    data <- read.table("rawdata.csv", header=TRUE, sep=",", na.strings = "99")

There are 415 columns with headers in format Q001, Q002, etc There are approximately 200 rows with no row labels/no label column

Upvotes: 3

Views: 1180

Answers (1)

Andrie
Andrie

Reputation: 179578

You can do this without a loop, as follows:

names(data) <- 1:415

Let me illustrate with an example:

dat <- data.frame(a=1:4, b=2:5, c=3:6, d=4:7)
dat
  a b c d
1 1 2 3 4
2 2 3 4 5
3 3 4 5 6
4 4 5 6 7

Now rename the columns:

names(dat) <- 1:4
dat
  1 2 3 4
1 1 2 3 4
2 2 3 4 5
3 3 4 5 6
4 4 5 6 7

EDIT : How to access your new data

@Ramnath points out very accurately that you won't be able to access your data using dat$1:

dat$1
Error: unexpected numeric constant in "dat$1"

Instead, you will have to wrap the column names in backticks:

dat$`1`
[1] 1 2 3 4

Alternatively, you can use a combination of character and numeric data to rename your columns. This could be a much more convenient way of dealing with your problem:

names(dat) <- paste("x", 1:4, sep="")
dat
  x1 x2 x3 x4
1  1  2  3  4
2  2  3  4  5
3  3  4  5  6
4  4  5  6  7

Upvotes: 3

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