Using paste to create and evaluate a variable expression
On Sep 16, 2012, at 9:04 PM, Bryan Keller wrote:
Is it possible to use "paste" to write out an expression and evaluate it?
Of course. ?as.expression ?parse ?eval
Suppose I want to add two vectors X1 and X2, defined as follows:
X1 <- 1:6
X2 <- 6:1
If I write the following it looks like what I want but is a character:
noquote(paste(paste("X", 1, sep = ""), paste("X", 2, sep = ""), sep = "+"))
Instead of noquote, you might want to look at bquote.
Is there a way to tell R that I want to evaluate the text, not just print it out as a character?
Evaluate in what context? It looks as though you are building a formula.
parse(text= paste(paste("X", 1, sep = ""), paste("X", 2, sep = ""), sep = "+") )
expression(X1+X2)
David Winsemius, MD Alameda, CA, USA