NVD3 Line chart tics wrongly aligned to grid when using datetype on xAxis

3
votes

I am currently working with NVD3 using Angular Directive (angular-nvd3). I have a very simple line chart with very simple data.

The problem I have encountered now is that my data is wrongly aligned with the Axis. Example plunker available here: http://plnkr.co/edit/jWEYt6?p=preview ,

I am using dates on my xAxis, which are parsed using d3 library:

tickFormat: function(d) {return d3.time.format('%d/%m')(new Date(d))}

Description:

I would expect the xAxis labels to be correspondent to the grid.

In the example you can clearly notice that the xAxis is not evenly devided (values: 06/11, 08/11, 11/11, 13/11). So usually 2 days and sometimes 3 days :)

What is worse - the peaks are not matching the grid. Example: 06/11 tick is really not even close to the grid's line where I guess it is supposed to be.

I have also tried this on master's code from repo and it happens there too. There is a link in the HTML head section.

Is there a problem with my data, proper date formatting or something else? Thanks!

2
javascriptangularjsnvd3.jsangular-nvd3

2 Answers

6
votes

This bugged me for a while and I could not find an answer here. I even have opened a bug on GitHub: https://github.com/novus/nvd3/issues/1382#issuecomment-160694559 and I was clued in on the answer.

The problem:

The actual issue is hidden because of d3.time.format('%d/%m'). My example data is given in one tick per day manner, and the format was set accordingly. But d3 does not understand that. When drawing the grid it divides the max-min/someValue and the grid ticks does not have to occur on full day (midnight), but on any hour. And because of the formatting I could not see that.

The version showing this misconception is here: http://plnkr.co/edit/2iMHOp?p=preview

Solution:

So now, when I know what I could do, I managed to substitute the ticks by using tickValues parameter in nvd3 / angular wrapper. The version with the solution is here: http://plnkr.co/edit/23n3ll?p=preview

Yet another bug :)

Funny thing is that since the labels are too long to be displayed, I had to rotate them so they could fit. Another bug occurs here (I think). As you can see 2nd and last but one tick label is missing. First I tried using the solution mentioned here: NVD3 Line Chart X Axis Ticks Are Missing using the showMaxMin parameter but it does not work correctly. But if you rotate the labels to ~ -70 degrees the labels are displayed OK.

I guess this is not the end with my NVD3 journey ;)

3
votes

Since the problem is, according to Atais:

The actual issue is hidden because of d3.time.format('%d/%m'). My example data is given in one tick per day manner, and the format was set accordingly. But d3 does not understand that. When drawing the grid it divides the max-min/someValue and the grid ticks does not have to occur on full day (midnight), but on any hour. And because of the formatting I could not see that.

I managed to pass the x's values as integer values (ex: 20160211) instead of formatted dates (ex: 2016-02-11 or similars) to nvd3, and then on tickFormatformat them to display properly.

I wrote another plunker with the problem and the commented solution (used momentjs):

Plunker with the simulated error: http://plnkr.co/edit/fXDQ0f?p=preview

Data is provided in format x: milliseconds, y: int, like {x: 1446418800000, y: 20}, and it is being formated with tickFormat:

  xAxis: {
    tickFormat: function(d) {
      return moment(d).format('YYYY-MM-DD');
    }
  }

Plunker with the solution: http://plnkr.co/edit/KpALzo?p=preview

Data is provided in format x: int, y: int, like {x: 20160211, y: 20}, and it is being formated with tickFormat:

  xAxis: {
    tickFormat: function(d) {
      moment(d, 'YYYYMMDD').format('YYYY-MM-DD');
    }
  }

Note that you can do it with time too, just by appending to the 'numeric date'.

As stated from @ajaybc, will not work well with dates from different months, since d3 will interpolate X axis with invalid filling dates (days 32, 33, 34 and so on)