Function for accessing regression output

Question

I just wrote this function for personal use only while working on a specific data project. I would be grateful for any feedback!

get.coef1 <- function(x) {
  x <- as.character(x)
  m.names <- paste("fit", x, letters[1:3], sep="")
  models3 <- matrix(numeric(12L), 3, 4)
  for (i in 1:3) {
    models3[i, ] <- summary(get(m.names[i]))$coefficients[2,]
  }
  return(models3)
}

Data to reproduce function above:

x <- rnorm(100)
y <- x^2/4
z <- rnorm(100)+y/100
w <- rnorm(100)

Edit1: And three fitted regressions:

fit3a <- lm(y ~ x)
fit3b <- lm(y ~ x + z)
fit3c <- lm(y ~ x + z + w)

Whose coefficients on x I want to access viaget.coef1(3).

Answer 1

Your function has several problematic assumptions for the object names in the environment (get()) and the number of objects (fixed length in the for loop).

In base R it would be more idiomatic and flexible to use some function from the *apply family, which operate on a list of objects, e.g.

do.call(rbind, lapply(list(fit3a, fit3b, fit3c),
                      function(x) summary(x)$coefficients["x", ]))
     Estimate Std. Error t value Pr(>|t|)
[1,]  0.01512    0.02927  0.5164   0.6067
[2,]  0.01530    0.02985  0.5127   0.6093
[3,]  0.01732    0.02899  0.5975   0.5516

t(sapply(list(fit3a, fit3b, fit3c),
         function(x) summary(x)$coefficients["x", ]))
     Estimate Std. Error t value Pr(>|t|)
[1,]  0.01512    0.02927  0.5164   0.6067
[2,]  0.01530    0.02985  0.5127   0.6093
[3,]  0.01732    0.02899  0.5975   0.5516

Output of get.coef1(3) (with set.seed(1)):

        [,1]    [,2]   [,3]   [,4]
[1,] 0.01512 0.02927 0.5164 0.6067
[2,] 0.01530 0.02985 0.5127 0.6093
[3,] 0.01732 0.02899 0.5975 0.5516