improve rain chart rounding

cmd/ingestd/web/app.js

@@ -101,6 +101,7 @@ function computeRainIncrements(points) {
     if (prev !== null) {
       delta = p.rain_mm - prev;
       if (delta < 0) delta = 0;
+      if (delta < 0.1) delta = 0;
     }
     prev = p.rain_mm;
     out.push({ x: t, y: delta });
@@ -118,7 +119,17 @@ function computeHourlySums(points, tz) {
   }
   return Array.from(buckets.entries())
     .sort((a, b) => a[0] - b[0])
-    .map(([x, y]) => ({ x, y }));
+    .map(([x, y]) => ({ x, y: y < 0.1 ? 0 : y }));
+}
+
+function clampRainSeries(points, key) {
+  return points.map((p) => {
+    const v = p[key];
+    if (v == null) {
+      return { ...p };
+    }
+    return { ...p, [key]: v < 0.1 ? 0 : v };
+  });
 }
 
 function startOfDay(date, tz) {
@@ -754,11 +765,14 @@ function renderDashboard(data) {
 
   const rainIncs = computeRainIncrements(obsFiltered);
   const rainHourly = computeHourlySums(rainIncs, state.tz);
+  const latestRainHour = rainHourly.length ? rainHourly[rainHourly.length - 1].y : null;
+  updateText("live-rain-hour", latestRainHour == null ? "--" : `${formatNumber(latestRainHour, 2)} mm`);
   const rainTitle = document.getElementById("chart-rain-title");
   if (rainTitle) {
     rainTitle.textContent = "Rain (obs hourly sum vs forecast)";
   }
 
+  const forecastRain = clampRainSeries(forecastLine, "precip_mm");
   const rainChart = {
     data: {
       datasets: [
@@ -772,7 +786,7 @@ function renderDashboard(data) {
         {
           type: "bar",
           label: "forecast precip (mm)",
-          data: series(forecast, "precip_mm"),
+          data: series(forecastRain, "precip_mm"),
           backgroundColor: colors.forecast,
           yAxisID: "y",
         },