Show average of dygraph points, which dynamically amends as the user zooms

问题

I have seen this - Horizontal line to show average in dygraph - and it doesn't quite answer my question.

I have the following simple dygraph:

g2 = new Dygraph(
  document.getElementById("graphdiv2"),
  "../newDataFile.csv",
  { ... }
);

where newDataFile.csv has two columns.

What I would like to show is the average of the points plotted (as a line or just a number), and for this average to change as I zoom in to different parts of the graph. Any ideas?

回答1:

var idx=1; //change this value if you have several plots.
var data = g2.rawData_;
var sum = data.map(function(e){return e[idx]})
              .reduce(function(a,b){return a+b});
var average = sum/data.length;

If you want to keep only values displayed if the graph is zoomed :

var idx=1; //change this value if you have several plots.
var data = g2.rawData_.slice(g2.boundaryIds_[idx][0],g2.boundaryIds_[idx][1]+1);
var sum = data.map(function(e){return e[idx]})
              .reduce(function(a,b){return a+b});
var average = sum/data.length;

来源：https://stackoverflow.com/questions/27918591/show-average-of-dygraph-points-which-dynamically-amends-as-the-user-zooms