Choropleth attempt

Tried implementing choropleth while keeping filters and adding zoom function. Zoom & drag function currently active on ALL graph types. Looking to keep zoom & drag only on choropleth

index.html

@@ -10,6 +10,9 @@
   <!-- D3.js library -->
   <script src="https://d3js.org/d3.v7.min.js"></script>
 
+  <!-- TopoJSON client library for map rendering -->
+  <script src="https://unpkg.com/topojson-client@3"></script>
+
   <!-- Save SVG as PNG library -->
   <script src="https://cdnjs.cloudflare.com/ajax/libs/save-svg-as-png/1.4.17/saveSvgAsPng.min.js"></script>
 </head>

script/script.js

@@ -83,8 +83,19 @@ darkModeToggle.addEventListener('click', () => {
 });
 
 
-// Load data
-d3.csv("PHSwithContinent.csv").then(function(data) {
+// Add 'choropleth' to chart type selector on page load
+if (document.getElementById("chartTypeSelect") && !Array.from(document.getElementById("chartTypeSelect").options).some(opt => opt.value === "choropleth")) {
+  const option = document.createElement("option");
+  option.value = "choropleth";
+  option.text = "Choropleth Map";
+  document.getElementById("chartTypeSelect").appendChild(option);
+}
+
+// Load both CSV and TopoJSON data
+Promise.all([
+  d3.csv("PHSwithContinent.csv"),
+  d3.json("script/countries-50m.json")
+]).then(function([data, world]) {
   // Normalize Socio-economic status values to match educationLevels
   data.forEach(d => {
     if (d["Socio-economic status"] === "Pre-primary, primary and lower secondary education") {
@@ -96,6 +107,7 @@ d3.csv("PHSwithContinent.csv").then(function(data) {
     }
   });
   const allData = data;
+  const worldData = world;
 
   // Populate continent and education dropdowns
   const continents = Array.from(new Set(data.map(d => d.CONTINENT))).sort();
@@ -166,6 +178,8 @@ d3.csv("PHSwithContinent.csv").then(function(data) {
       drawDotPlot(filteredData);
     } else if (selectedChart === "heatmap") {
       drawHeatmap(filteredData);
+    } else if (selectedChart === "choropleth") {
+      drawChoropleth(filteredData, worldData);
     }
   }
 
@@ -524,4 +538,97 @@ function drawHeatmap(data) {
 
   g.append("g")
     .call(d3.axisLeft(y));
+}
+
+// Choropleth map drawing function
+function drawChoropleth(data, worldData) {
+  // Remove any previous zoom behavior
+  svg.on("mousedown.zoom", null).on("touchstart.zoom", null).on("touchmove.zoom", null).on("touchend.zoom", null);
+
+  // Setup projection and path
+  const projection = d3.geoMercator()
+    .fitSize([width, height], topojson.feature(worldData, worldData.objects.countries));
+  const path = d3.geoPath().projection(projection);
+
+  // Prepare a map from country name to value
+  const valueByCountry = {};
+  data.forEach(d => {
+    valueByCountry[d["Reference area"]] = parseFloat(d.OBS_VALUE);
+  });
+
+  // Color scale for choropleth
+  const colorScale = d3.scaleSequential()
+    .interpolator(d3.interpolateYlGnBu)
+    .domain([0, 100]);
+
+  // Remove previous map if any
+  g.selectAll(".country").remove();
+  g.selectAll(".choropleth-legend").remove();
+
+  // Draw countries
+  const countries = topojson.feature(worldData, worldData.objects.countries).features;
+  const countryPaths = g.selectAll(".country")
+    .data(countries)
+    .join("path")
+    .attr("class", "country")
+    .attr("d", path)
+    .attr("fill", d => {
+      const name = d.properties.name;
+      const val = valueByCountry[name];
+      return val != null ? colorScale(val) : "#ccc";
+    })
+    .attr("stroke", darkMode ? "#222" : "#fff")
+    .attr("stroke-width", 0.5)
+    .on("mouseover", function(event, d) {
+      const name = d.properties.name;
+      const val = valueByCountry[name];
+      tooltip.html(`<strong>${name}</strong><br/>${val != null ? val + "%" : "No data"}`)
+        .style("left", (event.pageX + 10) + "px")
+        .style("top", (event.pageY - 40) + "px")
+        .transition().duration(300)
+        .style("opacity", 1)
+        .style("transform", "translateY(-10px)");
+    })
+    .on("mouseout", function() {
+      tooltip.transition().duration(500)
+        .style("opacity", 0)
+        .style("transform", "translateY(0px)");
+    });
+
+  // Add zoom and pan
+  svg.call(d3.zoom()
+    .scaleExtent([1, 8])
+    .on("zoom", (event) => {
+      g.attr("transform", event.transform);
+    })
+  );
+
+  // Add legend for color scale
+  const legendWidth = 200;
+  const legendHeight = 12;
+  const legendSvg = g.append("g")
+    .attr("class", "choropleth-legend")
+    .attr("transform", `translate(${width - legendWidth - 20},${height - 40})`);
+
+  const defs = svg.select("defs").empty() ? svg.append("defs") : svg.select("defs");
+  defs.selectAll("#choropleth-gradient").remove();
+  const linearGradient = defs.append("linearGradient")
+    .attr("id", "choropleth-gradient");
+  linearGradient.selectAll("stop")
+    .data(d3.range(0, 1.01, 0.01))
+    .enter().append("stop")
+    .attr("offset", d => d)
+    .attr("stop-color", d => colorScale(d * 100));
+
+  legendSvg.append("rect")
+    .attr("width", legendWidth)
+    .attr("height", legendHeight)
+    .style("fill", "url(#choropleth-gradient)");
+
+  // Legend axis
+  const legendScale = d3.scaleLinear().domain([0, 100]).range([0, legendWidth]);
+  const legendAxis = d3.axisBottom(legendScale).ticks(5).tickFormat(d => d + "%");
+  legendSvg.append("g")
+    .attr("transform", `translate(0,${legendHeight})`)
+    .call(legendAxis);
 }