Turning Data Frame Columns into Vectors
You access columns of a data.frame by column indices as in: X[ ,1], X[ ,2], etc. The index before the comma would stand for the row if you wanted to restrict those. The index after the comma captures the column. That said, you typically would not "extract" rows from the data frame but draw directly from the data frame for an analysis contingent on the factors in column 1. You may want to look at the tapply() function, in particular. HTH, Daniel
jawbonemurphy wrote:
Hi, I converted an Excel file into a .txt file "X.txt" with no header ( http://r.789695.n4.nabble.com/file/n3908157/X.txt X.txt ) and imported it with: X <- read.table("/Users/johnlogandurland/Desktop/X.txt", header=FALSE). What I would like to do is to make the first column into a factors vector, and then analyze the rest of the columns in the data table using those factors. The problem is, I haven't found a way to convert the rest of the columns into vectors with length = nrows so I can apply the factors vector to them. When I try: vect <- X[1] I get an object with class "data.frame" and length 1, and the "[[]]" command seems to turn the column into a "factor" vector, though with the right length. This seems like it should be a really easy thing to do, but I've looked through R-intro and been unable to find a good answer. Any ideas? Many Thanks, Logan
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