Pass null values to SVG path (using d3.js) to supp

问题:

Using jQuery Flot, I can pass a null value to the plotting mechanism so it just won't draw anything on the plot. See how the missing records are suppressed:

I'm looking to move to d3js, so that I can have deeper low level control of the graphics using SVG. However, I have yet to find out how to do that same process of suppressing missing records. The image below is an attempt to do this, using a value of 0 instead of null (where the d3 package breaks down). Here is some code to give you an idea of how I produced the graph below:

var line = d3.svg.line()
    .x(function(d) {
       var date = new Date(d[0]);
       return x(date);
    })
    .y(function(d) {
       var height = d[1]; 
       if (no_record_exists) {
           return y(0);
       }
       return y(height) + 0.5;
    });

I looked up the SVG path element at the Mozilla Developer Network, and I found out that there is a MoveTo command, M x y, that only moves the "pen" to some point without drawing anything. Has this been implemented in the d3js package, so that I won't have to create several path elements every time I encounter a missing record?

回答1:

The defined function of d3.svg.line() is the way to do this

Let's say we want to include a break in the chart if y is null:

line.defined(function(d) { return d.y!=null; })

回答2:

Use line.defined or area.defined, and see the Area with Missing Data example.