From 2c021a493e94db77cf6e6e4d7c0dfe64f0261730 Mon Sep 17 00:00:00 2001
From: Elio Campitelli <eliocampitelli@gmail.com>
Date: Tue, 24 Sep 2024 13:55:23 +1000
Subject: [PATCH] Adds unexported/experimental WriteNetCDF

---
 R/WriteNetCDF.R | 82 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 R/WriteNetCDF.R

diff --git a/R/WriteNetCDF.R b/R/WriteNetCDF.R
new file mode 100644
index 00000000..70f5a429
--- /dev/null
+++ b/R/WriteNetCDF.R
@@ -0,0 +1,82 @@
+WriteNetCDF <- function(data, file, vars, dims = NULL) {
+
+    if (is.null(names(vars))) {
+        names(vars) <- vars
+    }
+
+    if (any(!names(vars) %in% colnames(data))) {
+        stop("vars not found in data")
+    }
+
+    if (is.null(dims)) {
+        dims <- setdiff(colnames(data), names(vars))
+    }
+
+    if (is.null(names(dims))) {
+        names(dims) <- dims
+    }
+
+    if (any(!names(dims) %in% colnames(data))) {
+        stop("dims not found in data")
+    }
+
+    nc_dims <- vector(length(dims), mode = "list")
+    for (d in seq_along(dims)) {
+        vals <- as.numeric(unique(data[[names(dims)[d]]]))
+        n <- length(vals)
+        units <- get_units(data[[names(dims)[d]]])
+        nc_dims[[d]] <- ncdf4::ncdim_def(name = dims[d],
+                                         units = units,
+                                         vals = vals,
+                                         unlim = FALSE,
+                                         create_dimvar = TRUE,
+                                         calendar = NA,
+                                         longname = dims[d])
+    }
+
+    missing_value <- -999
+    nc_vars <- vector(length(vars), mode = "list")
+    for (v in seq_along(vars)) {
+        nc_vars[[v]] <- ncdf4::ncvar_def(name = vars[v],
+                                         units = "",
+                                         dim = nc_dims,
+                                         longname = vars[v],
+                                         missval = missing_value)
+
+    }
+
+    nc_file <- nc_create(file, nc_vars)
+
+    for (v in seq_along(vars)) {
+        ncdf4::ncvar_put(nc_file,
+                         varid = nc_vars[[v]],
+                         vals = field[[names(vars[v])]])
+    }
+
+    ncdf4::nc_close(nc_file)
+
+    return(invisible(file))
+}
+
+
+get_units <- function(x) {
+    UseMethod("get_units")
+}
+
+get_units.default <- function(x) {
+    return("")
+}
+
+get_units.Date <- function(x) {
+    return("days since 1970-01-01 00:00:00")
+}
+
+get_units.POSIXlt <- function(x) {
+    return("seconds since 1970-01-01 00:00:00")
+}
+
+get_units.POSIXct <- function(x) {
+    return("seconds since 1970-01-01 00:00:00")
+}
+
+