D3 ticks() does not return value if provided scale has only 1 result

Question

I have an x-axis that displays the days that my data occurs on. The data is dynamic and sometimes I have data for only 1 day, 2 days, n days, etc.

Here is my code for di

Answer 1

.ticks() should be used to set the number of ticks you'd like to have on your axis, not the kind of data that should be in them. So try to set it like .ticks(3) and it should set a couple of ticks.
From the wiki:
.ticks([count])
Returns approximately count representative values from the scale's input domain. If count is not specified, it defaults to 10. The returned tick values are uniformly spaced, have human-readable values (such as multiples of powers of 10), and are guaranteed to be within the extent of the input domain. Ticks are often used to display reference lines, or tick marks, in conjunction with the visualized data. The specified count is only a hint; the scale may return more or fewer values depending on the input domain.

Answer 2

Can you show how chart.x is set up? Hard to tell without seeing it, but you may be able to fix it by calling chart.x.nice() (see documentation).

Otherwise, seems like you'll need to manually check the extents of its domain, and adjust them in the case of single day.

Clarification

Your code shows how you call range() but not how you call domain(), which is the important one.

It seems to me to me that if do

var domain = chart.x.domain()
console.log domain[0] == domain[1]

you'll see true getting logged whenever the data is for only one day. If so, it means you're dealing with a single point in time rather than a time range. In that case, you'll need to adjust the domain to be a longer range.

Really hard to know without even seeing an image of what you're working on.

Answer 3

To extend the domain so that the scale starts and ends at a tick mark you use the .nice() method, as @meetamit suggested -- but "nicing" only works if you call that method after you set the domain, so that's why you might not have noticed any change. The API doesn't really make that clear, although since the method alters the domain I suppose it makes sense that changing the domain later would over-ride the effect of a previous nice() call.

Also, be sure to use the time-scale version of the method: .nice(d3.time.day) to get a domain rounded off to the nearest day as opposed to just the nearest hour.

Here's a fiddle:
http://fiddle.jshell.net/4rGQq/

The key code is simply:

xScale.domain(d3.extent(d)) 
      //d3.extent() returns max and min of array, which become the basic domain
      .nice(d3.time.day);  
      //nice() extends the domain to nearest start/end of a day

Compare what happens if you comment out the .nice() call after setting the domain, even with the other .nice() call during initialization of the scale. Also compare what happens if you don't specify the day-interval as a parameter to the nice method.