change CSV headers and column order, add comments

Author: abyrd

src/main/java/com/conveyal/analysis/results/TemporalDensityCsvResultWriter.java

@@ -31,15 +31,15 @@ public CsvResultType resultType () {
     public String[] columnHeaders () {
         List<String> headers = new ArrayList<>();
         // The ids of the freeform origin point and destination set
-        headers.add("originId");
-        headers.add("destId");
+        headers.add("origin");
+        headers.add("destinations");
         headers.add("percentile");
+        // The number of minutes needed to reach d destination opportunities
+        headers.add("D" + dualThreshold);
+        // The opportunity density during each of 120 minutes
         for (int m = 0; m < 120; m += 1) {
-            // The opportunity density over travel minute m
             headers.add(Integer.toString(m));
         }
-        // The number of minutes needed to reach d destination opportunities
-        headers.add("D" + dualThreshold);
         return headers.toArray(new String[0]);
     }
 
@@ -67,20 +67,24 @@ public Iterable<String[]> rowValues (RegionalWorkResult workResult) {
                 List<String> row = new ArrayList<>(125);
                 row.add(originId);
                 row.add(task.destinationPointSetKeys[d]);
-                row.add(Integer.toString(p));
-                // One density value for each of 120 minutes
+                row.add(Integer.toString(task.percentiles[p]));
+                // One column containing dual accessibility value
                 double[] densitiesPerMinute = percentilesForDestPointset[p];
-                for (int m = 0; m < 120; m++) {
-                    row.add(Double.toString(densitiesPerMinute[m]));
-                }
-                // One dual accessibility value
                 int m = 0;
                 double sum = 0;
+                // Find smallest integer M such that we have already reached D destinations after M minutes of travel.
                 while (sum < dualThreshold && m < 120) {
                     sum += densitiesPerMinute[m];
                     m += 1;
                 }
+                // -1 indicates the threshold number of opportunities had still not been reached after the highest
+                // travel time cutoff specified in the analysis.
                 row.add(Integer.toString(m >= 120 ? -1 : m));
+                // One density value for each of 120 one-minute bins.
+                // Column labeled 10 contains the number of opportunities reached after 10 to 11 minutes of travel.
+                for (int m = 0; m < 120; m++) {
+                    row.add(Double.toString(densitiesPerMinute[m]));
+                }
                 rows.add(row.toArray(new String[row.size()]));
             }
         }