I'm trying to draw a difference chart (like this one) but using a more modular style.
So far, I've got as far as reading in two dummy CSV files, combining the data, generating a chart, and am now trying to just draw a single line from one part of the data, but I keep getting an error. The full code is available on bl.ocks.org.
The error is:
Error: Problem parsing d="M0,221.73913043478262LNaN,182.60869565217394LNaN,195.6521739130435LNaN,156.52173913043478L500,91.30434782608697L500,91.30434782608697LNaN,156.52173913043478LNaN,195.6521739130435LNaN,182.60869565217394L0,221.73913043478262Z"
which occurs when doing this:
g.select('.line').attr('d', line);
At that point (as seen in the console), data is:
[{"year":1999,"imports":15,"exports":19},{"year":2000,"imports":18,"exports":20},{"year":2001,"imports":17,"exports":30},{"year":2002,"imports":20,"exports":32},{"year":2003,"imports":25,"exports":9}]
xScale.range() is:
[0, 500]
xScale.domain() is:
[1999, 2003]
yScale.range() is:
[300, 0]
and yScale.domain() is:
[9, 32]
I'm guessing there's a simple error somewhere in there, meaning the wrong data is being used to draw the line, but after several hours trying to fix this, I can't see what I've done wrong.
You are using an ordinal scale, which doesn't interpolate between values. The domain of that scale consists of two elements, and it will map those to the two elements in the output range. That is, 1999 is mapped to 0 and 2003 is mapped to 500. For any other inputs, the scale will return NaN as the value isn't in its input domain.
You can fix this by specifying all the years you want mapped in the domain and the corresponding output values in the range. In your case, the easiest would be to use a linear scale though as that seems to be what you're assuming will happen with your current scale. You would simply need to replace the definition of the scale and how the range is set. This is what I have done here.
Alternatively, you could use a time scale as that would give you potentially better labels.
Related
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/.
When I apply a dimension filter to a dc.js graph, there are ugly lines where the line plummets
towards the y axis.
Is it possible in dc/d3 to not do this, i.e I would expect the graph to more resemble the following;
You can call defined directly on the dc created chart.
chart
.chart((c) ->
dc.lineChart(c)
.interpolate('linear')
.defined((d) ->
return !isNaN(d.y)
)
)
The condition !isNan(d.y) can be anything you like that evaluates to true/false.
Note that the d passed by defined is a d3 object and is worth inspecting.
Two possible solutions, depending whether you want the line connected or in sections:
Pre-filter the data so that instead of having groups that sum to zero, there aren't groups there at all. This will connect the points with a line segment over the missing data. https://github.com/dc-js/dc.js/wiki/FAQ#filter-the-data-before-its-charted
Use lineChart.defined to put gaps/breaks in the line where there is no data. https://github.com/dc-js/dc.js/blob/master/web/docs/api-latest.md#definedvalue
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.
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.
I'm using d3.js to make a simple line graph. I want to know if there's a way to create "holes" in the graph, that is, if the line can be interrupted or cut when there is no data available.
I'm looking into either delete the places I don't need from the domain, or setting the line weight to 0 in specific segments, but I can't find a way to do either of these.
Thanks for your help!
The D3 line generator has a built in function to do just this, line.defined. You can use this function to control where your line is defined and where it is not (like where you have missing data.) If you wanted to make your line undefined whenever the second value in the point array is a javascript NaN value, you could say:
line.defined(function(d) { return !isNaN(d[1]); });
Here is a good example of this in action.