Combining multiple data sets in R - r

Question

I am a complete beginner in R/ programming language. Right now I am trying to process hundreds of comma separated data files using R. For time series analyses, I need to concatenate the data sets sequentially. Unfortunately, the data files do not have a designated column with time stamp and have some header lines. For that, I am parsing the file creation time from the second line of the data file and adding timesteps based on the sampling frequency which can be found in the third line of the data file. Also, the sampling frequency will vary from files to files that can be identified from the regex patterns in filename. The first three header lines look like this:
SPU1 Monitor Data File
SPU Data Filename = 06Aug2021 ,07 -08 -28,s1c1h17.txt
Sample Frequency = 1
Or
SPU1 Traffic Data File
SPU Data Filename = 05Aug2021 ,02 -48 -14,s1c1p2311.txt
Sample Frequency = 20
I have tried the for loop as well as the lapply. When I am trying the for loop, the script only run once. When I am trying the lapply, I am getting the following message. What am I doing wrong?
[Error in file(file, "rt") : invalid 'description' argument
In addition: Warning messages:
1: In n.readLines(paste(filenames\[i\], sep = ","), header = FALSE, n = 1, :
file doesn't exist
2: In n.readLines(paste(filenames\[i\], sep = ",|\\s|-"), header = FALSE, :
file doesn't exist
Called from: file(file, "rt")][1]
Here is the code I am trying:
setwd("C:/Users/rottweiller/Desktop/Practicing R")
filenames <- list.files(path="C:/Users/rottweiller/Desktop/Practicing R", pattern="c1h|c1p", full.names=FALSE)
library(reader)
library(readr)
library(tidyverse)
AddTS <- function(filenames){
#frq1 <- parse_number(n.readLines(paste(filenames[i], sep = ","), header = FALSE, n = 1, skip = 2))
frq1 <- as.integer(gsub("\\D", "", n.readLines(paste(filenames[i], sep = ","), header = FALSE, n = 1, skip = 2)))
TL1 <- n.readLines(paste(filenames[i], sep = ",|\\s|-"), header = FALSE, n = 1, skip = 1)
SUTC1 <- lubridate::parse_date_time(gsub("\\s-|\\s", "",
stringr::str_extract(TL1, "[SPU Data Filename = ]?\\d{2}\\D{3}\\d{4}\\s\\,\\d{2}\\s-\\d{2}\\s-\\d{2}")), orders = "dmYHMS")
C1 <- as.data.frame(read.delim(filenames[i], header = FALSE, sep = ",", skip = 79))
C1[] <- lapply(C1, function(j) if(is.numeric(j)) ifelse(is.infinite(j), 0, j) else j)
TS1 <- SUTC1 + (1/frq1)*seq_len(nrow(C1))
Card1 <- cbind(TS1, C1)
}
combined <- dplyr::bind_rows(lapply(filenames, AddTS))
Or
[for(i in 1:length(filenames)){
frq1 <- parse_number(n.readLines(paste(filenames\[i\], sep = ","), header = FALSE, n = 1, skip = 2), trim_ws = TRUE)
TL1 <- n.readLines(paste(filenames\[i\], sep = ",|\\s|-"), header = FALSE, n = 1, skip = 1)
SUTC1 <- lubridate::parse_date_time(gsub("\\s-|\\s", "",
stringr::str_extract(TL1, "\[SPU Data Filename = \]?\\d{2}\\D{3}\\d{4}\\s\\,\\d{2}\\s-\\d{2}\\s-\\d{2}")),
orders = "dmYHMS")
C1 <- as.data.frame(read.delim(filenames\[i\], header = FALSE, sep = ",", skip = 79))
C1\[\] <- lapply(C1, function(j) if(is.numeric(j)) ifelse(is.infinite(j), 0, j) else j)
TS1 <- SUTC1 + (1/frq1)*seq_len(nrow(C1))
Card1 <- cbind(TS1, C1)
}][1]

Answer 1

It's a good starting step that you already know about regular expressions and recent R libraries.
You could do something like this:
purrr::map_dfr(filenames, function(f) {
lines <- readLines(file(f))
frq <- lines[3] %>%
str_replace(".*?(\\d*)$", "\\1") %>%
as.integer()
frq
SUTC <- lines[2] %>%
stringr::str_extract("[SPU Data Filename = ]?\\d{2}\\D{3}\\d{4}\\s\\,\\d{2}\\s-\\d{2}\\s-\\d{2}") %>%
lubridate::parse_date_time(orders = "dmYHMS")
SUTC
C <- lines[(which(lines == "end of text") + 2):length(lines)] %>%
textConnection() %>%
read.delim(header = FALSE, sep = ",") %>%
mutate(across(.fns = ~ if_else(. == Inf, 0, .)))
C
TS <- SUTC + seq_len(nrow(C)) / frq
bind_cols(file = f, TS = TS, C)
})