d3 area chart with yaxis starting from 0

<script>

// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 50},
    width = 460 - margin.left - margin.right,
    height = 400 - margin.top - margin.bottom;

// append the svg object to the body of the page
var svg = d3.select("#my_dataviz")
  .append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
    .append("g")
    .attr("transform",
          "translate(" + margin.left + "," + margin.top + ")");

//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/3_TwoNumOrdered_comma.csv",

  // When reading the csv, I must format variables:
  function(d){
    return { date : d3.timeParse("%Y-%m-%d")(d.date), value : d.value }
  },

  // Now I can use this dataset:
  function(data) {

    // Keep only the 90 first rows
    data = data.filter(function(d,i){ return i<90})

    // Add X axis --> it is a date format
    var x = d3.scaleTime()
      .domain(d3.extent(data, function(d) { return d.date; }))
      .range([ 0, width ]);
    svg.append("g")
      .attr("transform", "translate(0," + (height+5) + ")")
      .call(d3.axisBottom(x).ticks(5).tickSizeOuter(0));

    // Add Y axis
    var y = d3.scaleLinear()
      .domain([0, d3.extent(data, function(d) { return +d.value; })] )
      .range([ height, 0 ]);
    svg.append("g")
      .attr("transform", "translate(-5,0)")
      .call(d3.axisLeft(y).tickSizeOuter(0));

    // Add the area
    svg.append("path")
      .datum(data)
      .attr("fill", "#69b3a2")
      .attr("fill-opacity", .3)
      .attr("stroke", "none")
      .attr("d", d3.area()
        .x(function(d) { return x(d.date) })
        .y0( height )
        .y1(function(d) { return y(d.value) })
        )

    // Add the line
    svg.append("path")
      .datum(data)
      .attr("fill", "none")
      .attr("stroke", "#69b3a2")
      .attr("stroke-width", 4)
      .attr("d", d3.line()
        .x(function(d) { return x(d.date) })
        .y(function(d) { return y(d.value) })
        )

    // Add the line
    svg.selectAll("myCircles")
      .data(data)
      .enter()
      .append("circle")
        .attr("fill", "red")
        .attr("stroke", "none")
        .attr("cx", function(d) { return x(d.date) })
        .attr("cy", function(d) { return y(d.value) })
        .attr("r", 3)

})

</script>

<script>

// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 50},
    width = 460 - margin.left - margin.right,
    height = 400 - margin.top - margin.bottom;

// append the svg object to the body of the page
var svg = d3.select("#my_dataviz")
  .append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
    .append("g")
    .attr("transform",
          "translate(" + margin.left + "," + margin.top + ")");

//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/3_TwoNumOrdered_comma.csv",

  // When reading the csv, I must format variables:
  function(d){
    return { date : d3.timeParse("%Y-%m-%d")(d.date), value : d.value }
  },

  // Now I can use this dataset:
  function(data) {

    // Keep only the 90 first rows
    data = data.filter(function(d,i){ return i<90})

    // Add X axis --> it is a date format
    var x = d3.scaleTime()
      .domain([0, d3.extent(data, function(d) { return d.date; }]))
      .range([ 0, width ]);
    svg.append("g")
      .attr("transform", "translate(0," + (height+5) + ")")
      .call(d3.axisBottom(x).ticks(5).tickSizeOuter(0));

    // Add Y axis
    var y = d3.scaleLinear()
      .domain( d3.extent(data, function(d) { return +d.value; }) )
      .range([ height, 0 ]);
    svg.append("g")
      .attr("transform", "translate(-5,0)")
      .call(d3.axisLeft(y).tickSizeOuter(0));

    // Add the area
    svg.append("path")
      .datum(data)
      .attr("fill", "#69b3a2")
      .attr("fill-opacity", .3)
      .attr("stroke", "none")
      .attr("d", d3.area()
        .x(function(d) { return x(d.date) })
        .y0( height )
        .y1(function(d) { return y(d.value) })
        )

    // Add the line
    svg.append("path")
      .datum(data)
      .attr("fill", "none")
      .attr("stroke", "#69b3a2")
      .attr("stroke-width", 4)
      .attr("d", d3.line()
        .x(function(d) { return x(d.date) })
        .y(function(d) { return y(d.value) })
        )

    // Add the line
    svg.selectAll("myCircles")
      .data(data)
      .enter()
      .append("circle")
        .attr("fill", "red")
        .attr("stroke", "none")
        .attr("cx", function(d) { return x(d.date) })
        .attr("cy", function(d) { return y(d.value) })
        .attr("r", 3)

})

</script>