V3: Line with gaps in data

HTML

<script src="http://www.amcharts.com/lib/3/amcharts.js"></script>
<script src="http://www.amcharts.com/lib/3/serial.js"></script>
<div id="chartdiv" style="width: 100%; height: 362px;"></div>

JavaScript

var chart;
var graph;

// note, some of tada points don't have value field
var chartData = [
    {
        "year": "1950",
        "value": -0.307
    },
    {
        "year": "1951",
        "value": -0.168
    },
    {
        "year": "1952",
        "value": -0.073
    },
    {
        "year": "1953",
        "value": -0.027
    },
    {
        "year": "1954",
        "value": -0.251
    },
    {
        "year": "1955",
        "value": -0.281
    },
    {
        "year": "1956",
        "value": -0.348
    },
    {
        "year": "1957",
        "value": -0.074
    },
    {
        "year": "1958",
        "value": -0.011
    },
    {
        "year": "1959",
        "value": -0.074
    },
    {
        "year": "1960",
        "value": -0.124
    },
    {
        "year": "1961",
        "value": -0.024
    },
    {
        "year": "1962",
        "value": -0.022
    },
    {
        "year": "1963",
        "value": 0
    },
    {
        "year": "1964",
        "value": -0.296
    },
    {
        "year": "1965",
        "value": -0.217
    },
    {
        "year": "1966",
        "value": -0.147
    },
    {
        "year": "1967"
    },
    {
        "year": "1968"
    },
    {
        "year": "1969"
    },
    {
        "year": "1970"
    },
    {
        "year": "1971",
        "value": -0.19
    },
    {
        "year": "1972",
        "value": -0.056
    },
    {
        "year": "1973",
        "value": 0.077
    },
    {
        "year": "1974",
        "value": -0.213
    },
    {
        "year": "1975",
        "value": -0.17
    },
    {
        "year": "1976",
        "value": -0.254
    },
    {
        "year": "1977",
        "value": 0.019
    },
    {
        "year": "1978",
        "value": -0.063
    },
    {
        "year": "1979",
        "value": 0.05
    },
    {
        "year": "1980",
        "value": 0.077
    },
    {
        "year": "1981",
        "value": 0.12
    },
    {
        "year": "1982",
        "value": 0.011
    },
    {
...