Question

Please download the file into your computer,and run :
http://freeuploadfiles.com/bb3cwypih2d2

data=read.table("path/to/file", sep="|",quote='',
       head=T,blank.lines.skip=T,as.is=T)
ddata=array(data,dim=c(nrow(data),ncol(data)))
ddata[1,1]

I want to extract the first element of the first column. The answer should be AAC.

How do I do that?

Answer 1

Some suggestions to clean your code and make life easier in the long term:

1. Work with the data in a data.frame, not an array.
2. Never refer to TRUE as T. TRUE is a reserved word that can never be redefined, whereas T can take any value, including FALSE
3. Use the <- symbol for assignment
4. Don’t use abbreviate argument names. The arguement is header, not head. This might bite you

Arrays can only contain a single class of object. Thus converting your data to array will implicitly convert the numeric column to character, which surely is a bad thing.

You then index the data frame like this:

dat <- read.table("nasdaqlisted.txt", sep="|", quote='',
                   header=TRUE, blank.lines.skip=TRUE, as.is=TRUE)

dat$Symbol[1]
[1] "AAC"

The following alternative ways of indexing also return the same element:

dat[1, "Symbol"]
dat[1, 1]
dat[, 1][1]
dat[["Symbol"]][1]

---

If you really want to do the foolish thing and convert your data to an array, then use matrix:

mdat <- as.matrix(dat)
mdat[1, 1]
Symbol 
 "AAC" 

Disclaimer: I only post this since you ask. Arrays and matrices are powerful and fast, but not appropriate for this data.