sql_load.R

#' SQL Load
#' 
#' This is function meant to be used along with ldply to read data in using sqldf.
#' 
#' @param x the path to a file to be read
#' @param selection the columns to return. Defaults to \code{"*"}
#' @param condition conditions defining which data rows to load in SQL
#' @param file.format an argument to be passed to \code{sqldf}. 
#' Defaults to assume a tab-delimited file with a header row.
#' See \code{?sqldf} for more info
#' 
#' @return A data frame
#' 
#' @export
#' @import sqldf

sql_load <- function(x, selection = "*", condition, file.format = list(header = TRUE, sep = "\t")){
  fi <- file(x)
  df <- sqldf(paste("select", selection, "from fi", condition, sep = " "), 
              file.format = file.format)
  close(fi)
  if(nrow(df)>0){
    df$File <- basename(x)
  }
  return(df)
}