I found that most of the examples of vega are illustrating creating charts which are with the x-axis, y-axis, title, and legends. There is even axis and scales defined in the specs. My question is:
Does vega support to create diagrams? such as UML editor?
In principle, I'd say yes - among the examples on the Vega website is a tree layout and a network layout. You could very likely adapt this to represent UML.
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Could you please help me to understand how can I create custom graphs (i.e. my own HTML+CSS) in Oracle BI?
I plan to design a dashboard and I need a very specific visualization (several interconnected circles segmented inside with fill % and color depending on different data sources) that is not available in stock graphs palette, and I can’t find any documentation on how to extend the palette.
It all depends on what technology you're aiming to you. Here's an example from ages ago about using D3js and calendar charts:
https://dimensionality.ch/2012/08/14/d3js-calendar-configuration-in-obiee-11g/
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I need to use JavaScript based charting library. There are lots of good JS library for charts:
D3.js
Google charts
ChartJS
n3-charts
EmberCharts
Meteor Charts
HighCharts
and so on....
While these libraries provide lots of options, it also creates confusion, it’s really hard to pick right chart for your data.
I have following questions:
Is there any guideline for selecting charts based on data?
How do you categorize your data? I am getting JSON data from a web service, Data can be multi-dimensional. There is no restriction on no. of columns and no. of rows. If data is too large, does it make sense to prevent users from selecting some charts?
There's two ways to understand your question, and both involve very complex answers.
Choosing the right visualization
Whole books have been written on the topic. One of the best guides that I know of is SeeingData's Inside the Chart series. They have an article for each of the more common chart types (bar, pie or radar charts, scatterplots etc.), each detailing what you can see in it, what data it is for and what kind of information it can hide.
As a rule of thumb, if you have a lot of continuous data, like a time series, use a line chart. If you have few datapoints or the data is discrete, bar chart is there for you. Use stacked variants if you're presenting shares (although stacked line chart, or area chart tends to be hard to read). If presenting correlation, use a scatter plot. Changes and differences are best shown on a slope graph. Showing ratios of a single datapoint? If you have just two or three competing fields, use a pie chart, for more elements, a single stacked bar is usually a better choice.
There are more types of graphs, but unless your readers are adept in statistics, they probably won't be able to read them. Remember that it's your responsibility as an author to choose the correct graph type, which does not mislead the readers and which communicates the story of the data the best. Note that there might be more stories in one dataset, hence more graphs, more views of it.
A more general advice is: don't be creative. Good intentions (I want my chart to look cool) often lead to disasters, like this misleading Gun deaths in Florida chart. Just stick to the basics, don't do fancy faux 3D charts and let the data speak for themselves. As Edwart Tufte put it
Show data variation not just design variation
Choosing the right visualization library
Main factors are your requirements, complexity of the task and your coding skills. Google Charts is an online Excel, you click your mouse a couple of times and out comes a decent graph. However, your customization options are very limited, if you don't like the output, you'll have to look elsewhere.
D3.js on the other hand is a low-level tool with quite steep learning curve. It takes a better part of the day to make your first bar chart. Most important fact is, it's not a graphing library, it's data driven documents library. Yes, it does have some helper functions for graphs, but you have to construct them from scratch and it takes a lot of time and effort. You need to know your SVGs, HTML and CSS, as that's what you'll be manipulating. The reward is its extreme flexibility, you can make whole apps based on D3. With skill, it can completely replace jQuery. It's a lot more and a lot harder than a simple pie chart generator.
If a simple pie chart generator is what you want, but Google Charts don't offer the options you need, then the true graphing libraries like Highcharts are for you. They take data in a lot of formats, let you choose the basic output type (eg. pie vs. bar chart), do a little bit of customization and off you go. It's the middle ground.
I don't use the framework-specific libs like n3, Ember or Meteor charts, but I'd guess they fall closer to Highcharts than D3. Just check if all you need is to supply data and a configuration object, or if you're down to creating and setting up individual SVG DOM nodes.
Generally, if don't know what to choose, go from the least complex ones. Try to make it in Excel first. Then in Google charts. Then learn some JavaScript and try the Highcharts or your framework-specific library. And only if you still need more options go for the big guns like D3.
I am using NVD3.js and want to create following chart:
As you can see - bars are stacked, two axis and grouped by x-axis
Using multiChart I got :
It is stacked, two axis, but not grouped by x-axis.
Maybe I need to use different chart type - not multiChart, but I didn't find bar charts where are two y-axis.
1) How can I achieve this using NVD3.js?
2) If it can not be done in NVD3.js, then which solution I can properly integrate?
Thanks!
The NVD3 Javascript library is, to quote their website, "an attempt to build re-usable charts and chart components". It's creators have made a couple key decisions in order to emphasize the reusability of the charts:
They have focused on implementing standard chart designs (line graphs, bar graphs, scatterplots), but implemented in flexible, interactive ways.
They have used the same data structure requirement for all the graphs:
The main data array contains multiple data series, each of which represents a logical grouping of the data;
Each series is an array of individual data objects containing two or more variables.
All the graphs have a similar style and reuse important pieces of code.
The NVD3 library allows you to create a grouped bar chart or a stacked bar chart, and even a chart that interactively animates between the two.
Adapting that chart to create a stacked and grouped bar chart is not a simple task, in part because the data structure would be different. You would need a three-level data structure (series > sub-series > datapoints, representing groups > stacks > bars) instead of the two-level (series > datapoints) structure used by NVD3.
All is not lost, however. NVD3 is built on the d3 Javascript library. D3 is much more flexible and open-ended; it doesn't define specific chart types, it defines a way of manipulating a webpage to make it match your data. You can use it to create any type of chart that can be drawn with HTML or SVG. But of course, that means that it is much more work, since you have to explicitly create all the parts of the graph, and make all the design decisions yourself!
I strongly recommend, if you want to use d3, start with the basics in the tutorials list or one of the introductory books. However, you'll also want to check out the gallery of examples, and from there you'll find the following charts that will be of particular interest:
Mike Bostock's Stacked Bar Chart
Bostock's Grouped Bar Chart of the same data
Ali Gencay's adaptation of those examples to create a stacked, grouped bar chart
Once you have become familiar with building charts in d3, you may want to open up the NVD3 source code to see if you can borrow some of their reusable code components (being sure to respect their licence terms, of course). However, I would not recommend doing so as a beginner -- it is a lot of code, and uses a lot of complex techniques to put all the pieces together.
Any tips on how would I go about producing a stacked bar chart with multiple levels?
Similar to having floated divs that slip underneath. But I understand that svg doesn't have the concept of floating, so something more rigid based upon the svg width.
I've just finished "interactive data visualisations" book, which is great but I think I'm hitting on an advanced topic and I've had no luck in the d3 documentation so far.
I think I may of come up with the solution, or at least the direction.
This example: http://bl.ocks.org/mbostock/3888852 it is of pie charts but the principle is the same.
It shows that it can be separate diagrams i.e. separate svg elements. However they are still drawn out in one go with d3.js treating it as one big diagram.
I can then use normal css to lay it out, e.g. display:inline-block.
Thanks Lars for the indication that multiple charts would do it.
I'm thinking of what would be the right terms to use in the UI of my new program, when referring to graphical data representations - i.e., whether to call them "charts", "plots" or "graphs". I was wondering how these terms are different, and when is it appropriate to use each of them?
Chart: Bar, line, or pie charts.
(source: jpowered.com)
(source: jpowered.com)
Plot: X-Y plot or blueprints.
(source: grass.itc.it)
Graph: Nodes connected by edges.
(source: graphviz.org)
I feel your pain. Google searching on these words lately for software libraries was quite difficult due to the overlap in their usage.
Elementary school kids are taught that "graphs" are two dimensional grids used for "graphically" displaying math functions. Yet "graph theory" is about networks, not functions; see graphviz.
Business graphics calls a representation using symbols a "chart," such as a pie chart or bar chart, yet a stripchart is a type of plot.