Question

Not sure how to ask this, but i’ll give it a try:

I have 20 data.frames (e.g. 2006_1, 2006_2, 2007_1, 2007_2, …) that I imported from MS Access.

Each data.frame has 10 columns and approximately 3 millions rows.

The first column in each data.frame is named secuityName, which is a list of stock tickers followed by some tags.

I would like to upcase every row in the SecurityName column in every one of the 20 data.frames.

The structure follows:

2006_1

> **SecurityName**   **...**
> AAPL abcdef        **...**
> MSFT abcdef        **...**

2006_2

> **SecurityName**   **...**
> AAPL abcdef        **...**
> MSFT abcdef        **...**

I would like each one to look like this:

2006_1

> **SecurityName**   **...**
> AAPL ABCDEF        **...**
> MSFT ABCDEF        **...**

I have a vector named *Raw_data_vector* that has all the data.frame names

Raw_data_vector

> 2006_1
> 2006_2
> 2007_1
> 2007_2
> ...

I have tried to use lapply but can’t get it to work:

lapply(1:length(Raw_data_vector), function(x) toupper(get(x)[,1]),Raw_data_vector)

Answer 1

This should get you started. I used data.frames that have characters that start their names so I don’t wind up with any funny business.

oh6_1 <- data.frame(SecurityName=letters[1:20], v=1:20)
oh6_2 <- oh6_1

out <- lapply(ls(pattern = 'oh[0-9]_*'), 
              function(x) {
                df <- get(x)
                df[, 1] <- toupper(df[, 1])  
                return(df)
              })

Per the comments:

Depending on the names of your data.frames, you’ll need to alter the pattern argument to ls. Also, R doesn’t change things in place (for the most part) instead it creates a new one.

You are seeing it as output to the console because it isn’t assigned to anything! Instead use something like out <- llply(ls(...)...). Then inspect out. It will be a list of the data frames you supplied with their additional column. You can inspect R objects with ?str.

Finally, this list of objects notion is a common result when working with many similar (or identical) things. It is easy from here to continue doing whatever process you want, accept instead of calling function(data.frame) in something like a for loop, you can call lapply(list of data frames, function)

… Clear as mud to be sure.

If you must do the lowercase operation to the existing data.frame, you can use the always scary assign function:

myfun <- function(X) {
  df <- get(x)
  df[, 1] <- toupper(df[, 1])
  assign(x, df, .GlobalEnv)
  return(NULL)
}

lapply(ls(), myfun)

now look at your data.frames.

> oh6_1
   SecurityName  v
1             A  1
2             B  2
3             C  3
4             D  4
5             E  5
6             F  6
7             G  7
8             H  8
9             I  9
10            J 10
11            K 11
12            L 12
13            M 13
14            N 14
15            O 15
16            P 16
17            Q 17
18            R 18
19            S 19
20            T 20
>