How to succinctly write a formula with many variables from a data frame?

Question

Suppose I have a response variable and a data containing three covariates (as a toy example):

y = c(1,4,6)
d = data.frame(x1 = c(4,-1,3), x2 = c(3,9,8), x3 =         


        

Answer 1

A slightly different approach is to create your formula from a string. In the formula help page you will find the following example :

## Create a formula for a model with a large number of variables:
xnam <- paste("x", 1:25, sep="")
fmla <- as.formula(paste("y ~ ", paste(xnam, collapse= "+")))

Then if you look at the generated formula, you will get :

R> fmla
y ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9 + x10 + x11 + 
    x12 + x13 + x14 + x15 + x16 + x17 + x18 + x19 + x20 + x21 + 
    x22 + x23 + x24 + x25