Fast way for splitting large .wav file using R - r

Question

For my work I need to analyze large .wav files (>208 MB), and I make use of the R packages seewave and tuneR. I bring each file into the R environment in 30 s chunks, using the readWave function as follows:
tr1_1 = readWave("TR1_edit.WAV", from = 0, to = 0.5, units = "minutes")
tr1_2= readWave("TR1_edit.WAV", from = 0.5, to = 1, units = "minutes")
tr1_3= readWave("TR1_edit.WAV", from = 1, to = 1.5, units = "minutes")
tr1_4= readWave("TR1_edit.WAV", from = 1.5, to = 2, units = "minutes")
tr1_5= readWave("TR1_edit.WAV", from = 2, to = 2.5, units = "minutes")
and so on. This method works, but is not efficient or pretty. Is there a way to import and split up a large .wav class file more efficiently?

Answer 1

If you're loading all of these into memory at the same time, rather than sequential variable names you should be using a list.
tr1 = list()
duration = 0.5
start_times = seq(0, 2, by = duration)
for (i in seq_along(start_times)) {
tr1[[i]] = readWave('TR1_edit.WAV',
from = start_times[i],
to = start_times[i] + duration,
units = 'minutes')
}
This is the same principle as why you should use a list of data frames rather than sequentially named data frames.
You could easily wrap this into a function that takes the name of a WAV file as input, gets its length from the metadata, and imports it in 30-second (or a parameterized argument) segments, and returns the list of segments.

Answer 2

#Gregor and #AkselA thanks for your input. The biggest issue with the for loop solution was that the wave files I'm working with are of varying sizes, so I would end up with blank elements in the resultant lists. My current solution imports the entire file, then breaks it up into 30s pieces from there:
duration = 1.44e6
tr1 <- readWave("TR1_edit.wav", from = 0, to = 1, units = "minutes")
tr1 <- as.matrix(tr1#left)
tr1 <- cbind(tr1, (rep(1:(length(tr1)/duration), each = duration)))
tr1 <- lapply(split(tr1[,1],tr1[,2]),matrix, ncol = 1)
From there I can use mapply to return the vectors to wave class
w <- function(s){
Wave(s, right = numeric(0), samp.rate = 48000, bit = 16, pcm = TRUE)
}
tr1 <- mapply(w, tr1)