as.data.frame.R

# Purpose        : Converts an object of type SoilProfileCollection to a single table;
# Maintainer     : Tomislav Hengl (tom.hengl@wur.nl); 
# Contributions  : Brendan Malone (brendan.malone@sydney.edu.au);
# Status         : pre-alpha
# Note           : see also "join" operation;


# Converts a SoilProfileCollection to a data frame:
.as.data.frame.SoilProfileCollection <- function(x, row.names = NULL, optional = FALSE, ...){
 
  ## derive layer sequence:
  s1 <- unlist(by(x@horizons[,x@depthcols[1]], x@horizons[,paste(x@idcol)], order))
  s2 <- unlist(by(x@horizons[,x@depthcols[2]], x@horizons[,paste(x@idcol)], order))
  HONU <- ifelse(s1==s2 & !x@horizons[,x@depthcols[1]]==x@horizons[,x@depthcols[2]], s1, NA) 

  ## Put all horizon in the same row:
  HOR.list <- as.list(rep(NA, summary(HONU)[[6]]))  ## highest number of layers
  for(j in 1:length(HOR.list)){
    HOR.list[[j]] <- subset(x@horizons, HONU==j)
    sel <- !{names(HOR.list[[j]]) %in% paste(x@idcol)}
    ## rename variables using a sufix e.g. "_A", "_B" etc:
    names(HOR.list[[j]])[sel] <- paste(names(HOR.list[[j]])[sel], "_", LETTERS[j], sep="")
  }

  ## Merge all tables (per horizon):
  HOR.list.m <- as.list(rep(NA, length(HOR.list)))
  for(j in 1:length(HOR.list)){
    sid <- data.frame(x@site[,paste(x@idcol)])
    names(sid) <- paste(x@idcol)
    HOR.list.m[[j]] <- merge(sid, HOR.list[[j]], all.x=TRUE, by=paste(x@idcol))
  }   

  ## Merge all horizon tables to one single table:
  tmp <- do.call(cbind, HOR.list.m)
  
  sel <- which(names(tmp) %in% paste(x@idcol))[-1] ## delete copies of IDs:
  tmp2 <- cbind(sp::coordinates(x@sp), x@site)
  fdb <- merge(tmp2, tmp[,-sel], all.x=TRUE, by=paste(x@idcol), ...)
  if(optional==TRUE){
    row.names(fdb) <- row.names
  }
   
  return(fdb)

}

setMethod('as.data.frame', signature(x = "SoilProfileCollection"), .as.data.frame.SoilProfileCollection)


## Reverse function -- extract horizons from a data.frame:
getHorizons <- function(x, idcol, sel, pattern=paste("_", LETTERS[1:15], sep="")){
  if(!length(unique(sel))==length(sel)){
    stop("'sel' argument must contain unique column names")
  }
  ## check that all horizon names from selection follow the pattern:
  t.lst <- expand.grid(sel, pattern, KEEP.OUT.ATTRS=FALSE, stringsAsFactors=FALSE)
  nn <- paste(t.lst[,1], t.lst[,2], sep="")
  h.lst <- as.vector(unlist(sapply(sel, FUN=function(l){grep(l, names(x))})))
  if(!all(names(x)[h.lst] %in% nn)){
    stop("Some column names do not follow the 'pattern'. Consider renaming.")
  }
  ## horizon list:
  h.lst <- lapply(sel, FUN=function(l){grep(l, names(x))})
  mm <- max(sapply(h.lst, length))
  m.lst <- rep(list(data.frame(x[,idcol])), mm)
  for(j in 1:mm){
    names(m.lst[[j]]) <- idcol
    for(i in sel){ 
      csel <- grep(paste(i, pattern[j], sep=""), names(x))
      if(length(csel)==1){
        m.lst[[j]][,i] <- x[,csel]
      }
    }
  }
  horizons <- do.call(plyr::rbind.fill, m.lst)
  return(horizons)
}


# end of script;