R: Regress all variables that match certain pattern

Question

Is there a way in R to add all variables into a regression that match a certain pattern? For example, I have a bunch of variables in my dataset that correspond to holidays with

Answer 1

A string can be turned into a formula.

data(iris)

fmla <- as.formula(paste("Species ~", 
               paste(grep("Width", names(iris), value = TRUE), collapse = " + ")))

glm(fmla, data = iris, family = binomial(link = "logit"))

Answer 2

To programmatically construct a formula, have a look at reformulate().

Here's an example that uses grep() to find all variables that begin with a "d" and then uses reformulate() to plug them in as the regressor variables on the RHS of a formula object.

vv <- grep("^d.*", names(mtcars), value=TRUE)
ff <- reformulate(termlabels=vv, response="mpg")
lm(ff, data=mtcars)
# 
# Call:
# lm(formula = ff, data = mtcars)
# 
# Coefficients:
# (Intercept)         disp         drat  
#    21.84488     -0.03569      1.80203