R/utils.R

In wearables: Tools to Read and Convert Wearables Data

#' as_time
#' @description Converts Unix time to as.POSIXct 
#' @param x takes a unixtime and converts to as.POSIXct
#' @param tz timezone is set to UTC
#' @export
# Convert time in seconds to a POSIXct.
as_time <- function(x, tz = "UTC"){
  as.POSIXct(x, origin = "1970-1-1", tz = tz)
}


#' prepend_time_column
#' @description Column binds a time_column to the dataframe
#' @param data dataframe
#' @param timestart the start of the recording
#' @param hertz hertz in which the E4 data was recorded
#' @param tz The timezone, defaults to user timezone
#' @export 
#' @importFrom lubridate with_tz
prepend_time_column <- function(data, timestart, hertz, tz = Sys.timezone()){

  datetime <-  as_time(timestart) + (1/hertz) * (1:nrow(data) - 1)

  datetime <- with_tz(datetime, tz)

  out <- cbind(data.frame(DateTime = datetime), data)

  return(out)
}

#' pad_e4
#' @description function to combine several e4 files, and sets the length of the x-axis
#' @param x index of dataframe
#' @export
#' @importFrom dplyr left_join
#' @importFrom stats median
#' @importFrom utils unzip
#' @importFrom utils read.csv
pad_e4 <- function(x){

  interval <- as.numeric(median(diff(x$DateTime)))

  out <- data.frame(DateTime = seq(from = min(x$DateTime),
                                   to = max(x$DateTime),
                                   by = interval)
  )

left_join(out, x, by = "DateTime")
}


# Are all provided data files filled? 
# Returns FALSE if one or more files have 1 or 0 lines of data.
check_datafiles_filled <- function(path){
  
  datasets <- c("EDA","ACC","TEMP","HR","BVP","IBI")
  fns <- file.path(path, paste0(datasets, ".csv"))
  
  nrows <- sapply(fns, R.utils::countLines)
  
  all(nrows > 1)
}