New function: get y-axis measurement unit symbol

Function provides a 'hack' that ensures that the correct phenomenon
symbols are displayed by a scatter plot's tooltip

public/js/src_modules/chartScatterPlot.mjs

@@ -177,6 +177,36 @@ const createSeriesOptionsForScatterPlot = function (
   }
 };
 
+/**
+ * Match a scatter plot's y-axis phenomenon name to its corresponding symbol
+ *
+ * @param {String} seriesName A string representing a scatter plot's series name. It is made up of two phenomenon names separated by a comma
+ * @returns {String} The phenomenon's symbol
+ */
+const getYAxisUnitOfMeasurementSymbol = function (seriesName) {
+  const phenomenonNameToSymbolMapping = {
+    temperature: "\u00B0C",
+    flow: "m\u00B3/h",
+    power: "kW",
+    energy: "MWh",
+  };
+
+  // The `series.name` property for the scatter plot is made up of
+  // two phenomenon names delimited by a comma
+  // We are interested in the first string
+  const phenomenonNameYAxis = seriesName.split(",")[0].toLowerCase();
+
+  if (phenomenonNameYAxis.includes("temperature")) {
+    return phenomenonNameToSymbolMapping.temperature;
+  } else if (phenomenonNameYAxis.includes("flow")) {
+    return phenomenonNameToSymbolMapping.flow;
+  } else if (phenomenonNameYAxis.includes("power")) {
+    return phenomenonNameToSymbolMapping.power;
+  } else if (phenomenonNameYAxis.includes("energy")) {
+    return phenomenonNameToSymbolMapping.energy;
+  }
+};
+
 /**
  * Draw a scatter plot using Highcharts library
  * @param {Array} formattedObsArrayForSeriesOnePlusSeriesTwo Response from SensorThings API formatted for use in a scatter plot
@@ -217,8 +247,7 @@ const drawScatterPlotHighcharts = function (
   );
 
   // The unit of measurement symbols for the x-axis is the first element of the array
-  // Assume that we will be comparing similar phenomena, so we can reuse this symbol
-  const UNIT_OF_MEASUREMENT_SYMBOL = unitOfMeasurementSymbolsArr[0];
+  const unitOfMeasurementXAxisSymbol = unitOfMeasurementSymbolsArr[0];
 
   const MARKER_RADIUS = 2;
 
@@ -302,9 +331,9 @@ const drawScatterPlotHighcharts = function (
 
         const pointString = `<b>${this.point.y.toFixed(
           2
-        )} ${UNIT_OF_MEASUREMENT_SYMBOL}, ${this.point.x.toFixed(
-          2
-        )} ${UNIT_OF_MEASUREMENT_SYMBOL}</b>`;
+        )} ${getYAxisUnitOfMeasurementSymbol(
+          this.series.name
+        )}, ${this.point.x.toFixed(2)} ${unitOfMeasurementXAxisSymbol}</b>`;
 
         return headerString + pointString;
       },