R/utilities.R

In ari: Automated R Instructor

is_Wave <- function(x){
  identical(suppressWarnings(as.character(class(x))), "Wave")
}

# get random string
grs <- function(){
  paste(sample(c(seq(10), letters, LETTERS), 
               size = 12, replace = TRUE), collapse = "")
}

# how long is a wav?
duration <- function(wav){
  stopifnot(is_Wave(wav))
  length(wav@left) / wav@samp.rate
}

# get from list
# list, name of element, default
gfl <- function(l, n, d){
  if(is.null(l[[n]])){
    d
  } else {
    l[[n]]
  }
}

#' @importFrom purrr map_chr compose
string_tirm <- function(s){
  str_rev <- function(t){
    paste(rev(strsplit(t, NULL)[[1]]), collapse = "")
  }
  
  str_trim_right <- function(x){
    sub("\\s+$", "", x)
  }
  
  str_trim_left <- function(x){
    x <- str_rev(x)
    x <- str_trim_right(x)
    str_rev(x)
  }
  
  lr <- compose(str_trim_left, str_trim_right)
  map_chr(s, lr)
}

# get text from html comments in an Rmd
parse_html_comments <- function(path){
  lines_ <- readLines(path, warn = FALSE)
  starts <- grep("<!--", lines_)
  ends <- grep("-->", lines_)
  
  if(length(starts) != length(ends)){
    stop("There's a comment open/close mismatch.")
  }
  
  result <- rep(NA, length(starts))
  
  for(i in seq_along(starts)){
    if(starts[i] == ends[i]){ # Single line
      result[i] <- lines_[starts[i]]
    } else {
      # Multiple lines
      result[i] <- paste(string_tirm(lines_[starts[i]:ends[i]]), 
                         collapse = " ")
    }
    result[i] <- sub("<!--", "", result[i])
    result[i] <- sub("-->", "", result[i])
  }
  
  string_tirm(result)
}

# split a big string into equal-ish sized pieces
#' @importFrom purrr map
split_up_text <- function(text){
  pieces <- ceiling(nchar(text)/1500)
  words <- strsplit(text, " ")[[1]]
  chunks <- split(words, ceiling(seq_along(words)/(length(words)/pieces)))
  map(chunks, paste, collapse = " ")
}