Combo Chart from Google Charts Library - google-visualization

Question

I am trying to use ComboCharts .
In its options variable, it sets a value 5 against series in example Here. What does this 5 mean ?
var options = {
title : 'Monthly Coffee Production by Country',
vAxis: {title: "Cups"},
hAxis: {title: "Month"},
seriesType: "bars",
series: {5: {type: "line"}}
};
Edit: I now realize that this 5 is the value types per value on vAxis
While I experimented, changing 5 to 0,1,2,3 or 4. It only changed the position of the line.
How is it related to position of line in the chart ?

Answer 1

The number there is the zero based index of the series in your data that you are changing the properties of. The seriesType: "bars" part in you options says all of your series will default to being rendered as bars.
When you specifically call out a series like that you are overriding the defaults. In this case you were saying that column 5 should be rendered as a line.
Take a look at this example to see the relationship between the series and the data.
google.load("visualization", "1", {
packages: ["corechart"]
});
google.setOnLoadCallback(drawChart);
function drawChart() {
var data = google.visualization.arrayToDataTable([
["X", "C1", "C2", "C3", "C4", "C5"],
["A", 1, 2, 3, 4, 5],
["B", 2, 5, 1, 7, 9],
["C", 6, 2, 4, 1, 8],
["D", 7, 1, 2, 3, 6]
]);
var options = {
seriesType: "bars",
series: {
// Make the first column (C1) a blue bar (bar because it is the default)
0: {
color: "blue"
},
// Make the fourth column (C4) a green line (line because we overrode the default)
3: {
type: "line",
color: "green"
}
}
};
var chart = new google.visualization.ComboChart(document.getElementById("chart"));
chart.draw(data, options);
}
<script type="text/javascript" src="https://www.google.com/jsapi"></script>
<div id="chart" style="width: 900px; height: 300px;"></div>