NVD3 - configuring ticks on axis - javascript

I have a nvd3 line chart which displays a time series and can't get the ticks on the x axis right.
For longer time spans, it works as expected. But for shorter time spans (here: 12/31/05 to 01/01/06), the same date is displayed for multiple ticks:
Please have a look at the code for this chart on JSFiddle
I want the chart to only display ticks at data points, and not in between. Is that possible with a line chart? From my understanding, it is possible with d3, but I can't figure out if this functionality is exposed by nvd3.
I've tried explicitly setting the number of ticks with chart.xAxis.ticks() without success. The only thing that has any effect is explicitly setting the tick values with chart.xAxis.tickValues([...]), but I would prefer not having to calculate them myself.

The way to solve this in general is with custom multi-scale time formats. Note that this example itself will not work with NVD3 because it uses an older version of D3, the examples below will though.
The problem in your case is that the ticks aren't "clean" divisions of time and if you apply a multi-scale format, you get something like this. It always shows the more fine-grained format because anything else would involve a loss of precision.
You can however use a simple heuristic to show the date instead of the time if the hour is less than 3, which works reasonably well in your case. See here for an example. The proper way to do this would be to make your ticks clean divisions.
Which brings us to your actual question. There's no other way than to explicitly set .tickValues() for what you want to do, but you can compute the x positions in your data quite easily:
var xvalues = [],
tmp = data.map(function(e) {
return e.values.map(function(d) { return d[0]; });
});
xvalues.concat.apply(xvalues, tmp);
The code is not the prettiest because it's a nested structure, but fairly straightforward. Using this, you can set your tick values explicitly, full example here.

Related

Parallel coordinates with d3.js

I need to to represent a Parallel Coordinates with d3.js. First of all I have no idea if what I think is possible to achieve (and if the Parallel Coordinates is the right chart).
I will explain my idea: I take data from a database and I expose them in a JSON and I store them in an array of objects (with JavaScript).
This is an example of the data http://pastebin.com/DZcMqDMc.
I would like to represent along the abscissa axis years (though there are years repeating themself, as you can see from data example), while along the ordinate axis values of those years (values are in percent, ranging from 1 to 100).
I would like to represent two lines according to "value1" and "value2" property in the JSON file.
Is it possible? Is Parallel Coordinates the right chart?
The main problem I have right now is that I do not understand how to set right the two domains (abscissa and ordinate).
I am basing on the example Parellel Coordinates of Bostock.
For abscissa I am thinking something like that:
x.domain(
d3.extent(test,
function(d) {
return d.years;
}
)
);
It makes sense or?
Try a multi line chart.That might suit your need.
I am not sure what you are trying.
Simply do a line chart, and produce the vertical lines by formatting the ticks to go from 0 to height ( in your var xAxis code include .tickSize(0-height)). You will have to pick the right number of ticks, as in ticks(), so you just get the lines where you want them.
Check out Parcoords, a d3-based parallel coordinates library. For compatibility with d3 v5 see https://github.com/BigFatDog/parcoords-es which is based on the original Parcoords library (https://github.com/syntagmatic/parallel-coordinates) which relies on an outdated version of d3.
For examples and sample code, check out the following link: http://syntagmatic.github.io/parallel-coordinates/.

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

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!
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 ;)
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)

d3.js scatter matrix with brushing - scale error

I try to reuse the example of 'scatter matrix with brushing': http://bl.ocks.org/mbostock/4063663
It seems that the code is not directly reusable with another csv. Scales seems to be somehow hard coded or so: i change the csv by adding 10 to 75% of the first column values, and the xscale is not directly updated.
To visualize the problem, see the fork of the mbostock gist: http://bl.ocks.org/fdeheeger/7249196
I cannot figure out where/how the scale is computed or updated in the javascript code.
Any advice from a d3 expert?
The scales are computed dynamically -- the problem is that the numbers in the CSV are parsed and processed as strings and not numbers. This is also the case in the original block, but there it doesn't matter because the ordering of the strings is the same as the ordering of the numbers.
All you need to do to fix this is parse the strings to numbers:
domainByTrait[trait] = d3.extent(data, function(d) { return +d[trait]; });
The plus makes all the difference here. Complete example here.

Adjusting Shield UI JavaScript chart when NULL values are present

I am using Shield UI JavaScript chart to show some monthly data to my visitors. However the available data doesn’t always equal 12 months. On the other hand I have categorical values on my X axis;
January, February and so on.
I am using a line chart type and for months where there are no adjacent values I do get a point which makes my chart to look some messy.
I tried to adjust the
seriesSettings: {
line: {
drawNullValues: true
}
}
property, however the look remains. Any ideas?
Since you have categorical values – the names of the 12 months, it wouldn’t make much sense using the drawNullValues. This is because once there is a values (even null) for a point, it takes it’s place on the X axis.
Your chart will look much better, if you use the appropriate type- let’s say bar so that data is easy to see and months with and without data will be easy to distinguish.

Charting thousands of points with dojo

I need to plot thousands of points, perhaps close to 50,000 with the dojo charting library. It works, but it's definitely very slow and lags the browser. Is there any way I can get better performance?
EDIT:
I solved by applying a render filter to the data. Essentially, I have a new item parameter called "render" which is set to false by my json source if the point is expected to overlap others. My DataSeries then queries for all points where render:true. This way all of the data is there still for non-visual sources that want all of the points, while my charts now run smoothly.
Psuedocode:
def is_overlapped(x, y, x_round, y_round)
rounded_x = round(x, x_round)
rounded_y = round(y, y_round)
hash = hash_xy(rounded_x, rounded_y)
if(#overlap_filter[hash].nil?)
#overlap_filter[hash] = true
return false
end
return true
end
x_round and y_round can be determined by the x and y ranges, say for example range / 100
I know this isn't probably exactly the answer you're looking for, but have you considered simply reducing the number of points you are plotting? I don't know the specific function of the graph(s), but I'd imagine most graphs with that many points are unnecessary; and no observer is going to be able to take that level of detail in.
Your solution could lie with graphing techniques rather than JavaScript. E.g. you could most likely vastly reduce the number of points and use a line graph instead of a scatter plot while still communicating similar levels of information to your intended target.

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