#' Plot water balance from NetCDF file
#'
#' Plots water balance calculated by GOTM ('Qres') and inflows from the netCDF output file.
#'
#' @param ncdf filepath; Name of the netCDF file to extract variable
#' @param title character; Title of the graph. Defaults to 'Water Balance
#' @return dataframe with the
#' @importFrom ncdf4 nc_open
#' @importFrom ncdf4 nc_close
#' @importFrom ncdf4 ncvar_get
#' @importFrom ncdf4 ncatt_get
#' @importFrom reshape2 melt
#' @import ggplot2
#' @export
plot_wbal <- function(ncdf, title = 'Water Balance'){
vars_short = list_vars(ncdf,long = F)
flows_nam = list(vars_short[grep('Q_', vars_short)])
fid = nc_open(ncdf)
tim = ncvar_get(fid, 'time')
tunits = ncatt_get(fid,'time')
#Extract time and formate Date
lnam = tunits$long_name
tustr <- strsplit(tunits$units, " ")
step = tustr[[1]][1]
tdstr <- strsplit(unlist(tustr)[3], "-")
tmonth <- as.integer(unlist(tdstr)[2])
tday <- as.integer(unlist(tdstr)[3])
tyear <- as.integer(unlist(tdstr)[1])
origin = as.POSIXct(paste0(tyear,'-',tmonth,'-',tday), format = '%Y-%m-%d', tz = 'UTC')
time = as.POSIXct(tim, origin = origin, tz = 'UTC')
flows = list()
#Extract flows
for(i in 1:length(flows_nam)){
eval(parse(text = paste0("flows[[",i,"]] <- ncvar_get(fid, '",flows_nam[[i]],"')")))
}
flows_df <- data.frame(matrix(unlist(flows)),stringsAsFactors=FALSE)
colnames(flows_df) <- flows_nam
#Extract GOTM water balance
qres = ncvar_get(fid, 'Qres')
qres = qres[nrow(qres),]
tunits = ncatt_get(fid, 'Qres')
nc_close(fid)
#Extract time and formate Date
df <- data.frame(DateTime = time, GOTM_calc = qres)
df <- cbind.data.frame(df, flows_df)
dfmlt <- reshape2::melt(df, id.vars = 'DateTime')
colnames(dfmlt) <- c('DateTime', 'Flow', 'value')
#Plot data
p1 <- ggplot(dfmlt, aes(DateTime, value, colour = Flow))+
geom_line(size = 0.8)+
ggtitle(title)+
xlab('')+
geom_hline(yintercept = 0, colour = 'black')+
ylab(tunits$units)+
theme_bw(base_size = 18)
p1
return(p1)
}
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