read_network(): aggregate volumes for multiple links

DESCRIPTION

 Package: mapMCDA
 Title: Produce an epidemiological risk map by weighting multiple risk
         factors
-Version: 0.4.45
+Version: 0.4.47
 Date: 2020-04-25
 Authors@R: c( person("Andrea", "Apolloni", email =
         "andrea.apolloni@cirad.fr", role = c("ctb"), comment = "Animal

R/network.R

@@ -126,8 +126,23 @@ must be respected:",
   
   ## Check duplicated edges
   if ( any(idx <- duplicated(dat[, 1:2])) ) {
-    print(dat[which(idx), 1:2])
-    stop("The links above appear more than once")
+    
+    if (nc == 6L) {
+      ## No volume. Just remove duplicated lines
+      dat <- dat[!duplicated(dat),]
+    } else {
+      ## Aggregate volume with warning
+      warning(
+        "Aggregating volumes for multiple links.",
+        "If this is not what you want, stop now and aggregate manually."
+      )
+      dat <- 
+        aggregate(
+          dat[,7],
+          by = dat[, 1:6],
+          FUN = "sum"
+        )
+    }
   }
   
   ## Check graph is directed

tests/testthat/test-load.R

@@ -92,3 +92,33 @@ test_that("Informative errors for incorrectly formatted network data", {
     "Expected 6 or 7 columns"
   )
 })
+
+test_that("read_network aggregates volume for multiple links", {
+  
+  base_df <- data.frame(
+    orig = rep(letters[1:4]),
+    dest = rep(letters[4:1]),
+    olon = rep(1:4),
+    olat = rep(1:4),
+    dlon = rep(4:1),
+    dlat = rep(4:1),
+    vol = 10*1:4,
+    stringsAsFactors = FALSE
+  )
+  
+  df <- rbind(base_df, base_df, base_df)
+  
+  tf <- tempfile(fileext = ".csv")
+  write.csv(df, file = tf, row.names = FALSE)
+  expect_warning(
+    res <- read_network(tf),
+    "Aggregating volumes"
+  )
+
+  expect_equal(
+    as_data_frame(res),
+    transform(base_df[, -(3:6)], vol = 3 * vol)[order(base_df$vol, decreasing = TRUE),],
+    check.attributes = FALSE
+  )
+  
+})