How can I output the processes within a function to a textfile in R (sink doesn't work when operations are run invisibly)?

Question

I am trying to write a function that performs several stepwise regressions and outputs the 'steps' of each one to a text file. The problem I am having is that sink() doesn't actually output anything since none of the operations in the function show up in the R console.

Edit: The problem actually seems to arise in the first part of my function. The file "model_log.txt" never even gets created, so something tells me sink won't work at all within a function.

This is my function so far:

stepModel <- function(formula, family = binomial, data, outfile = NULL) {
    if (is.null(outfile) == FALSE){
        sink(file = file.path(getwd(),"Reports/model_log.txt"),
            append = TRUE, type = "output")
        print("")
        print("Models run at:   ")
        print(Sys.time())
    }
    model.initial <- glm(formula, family = family, data = data)
    summary(model.initial)
    model.stepwise1 <- step(model.initial, direction = "backward")
    summary(model.stepwise1)
    model.stepwise2 <- step(model.stepwise1, scope = ~.^2)
    summary(model.stepwise2)
    if (is.null(outfile) == FALSE) sink()
    output <- list(modInitial = model.initial, modStep1 = model.stepwise1, modStep2 = model.stepwise2)
    return(output)
}

I am using the following dataframe to test my results (never mind that the stepwise regression removes everything but the intercept, this is enough for you to repeat my results):

test.df <- data.frame(a = sample(0:1, 100, rep = T),
                      b = as.factor(sample(0:5, 100, rep = T)),
                      c = runif(100, 0, 100),
                      d = rnorm(100, 50, 50))

test.mdl <- stepModel(a~., family = binomial, data = test.df, outfile = file.path(getwd(), "test_log.txt"))

I want this function to send all these steps to whatever file is specified in the outfile option. Any ideas?

Answer 1

made a mistake in the part that says:

 sink(file = file.path(getwd(),"Reports/model_log.txt"),
            append = TRUE, type = "output")

this should say:

sink(file = outfile,
            append = TRUE, type = "output")