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Comment by joshe | Hacker News Reader

Context is important, this is targeted at journalists. They are usually trying to make a point to casual readers.

For readers with more interest or who are numerate in their day jobs (engineers, finance, or economists), dual axis charts can often be a great choice.

This is better graph style advice from the Economist, which includes good dual axis examples and one bad one and how to correct it. https://medium.economist.com/mistakes-weve-drawn-a-few-8cdd8...

Since we are engineers or founders trying to deal with very complex systems, adding detail and clarity like the Economist or Edward Tufte does is the better way to go.

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Author here. Thanks for setting the context: Datawrapper – the data vis tool I write articles like this for – is indeed for people who want to make a point with their charts and maps, often to a broad audience. I agree that people who have learned to read dual axis charts can benefit greatly from them (the same is true for rainbow color maps).

Financial Times journalist John Burn Murdoch changed my mind on dual axes charts – even for casual readers! – a bit over the last six years, too. Here's a dual axis chart he created for the FT: https://x.com/AlexSelbyB/status/1529039107732774913

The next article I write on dual axis charts will probably be a "What to consider when you do use them" one.

Wow. That's a quite telling chart (and it's insane to me to think that 5% of total print articles would cover immigration).

At first glance, sure, but without further context or supporting data I'm suspicious:

   1. Why just the Daily Mail? Is that the only paper that matters in Britain, or just the one that happens to correlate?
   2. I would expect public opinion to lag coverage in the paper if there were a causal relationship. This graph is over too great a period to really see that, but if the creator wants to convince me, they'd show that.
   3. I might expect the lag to differ when coverage is increasing vs. decreasing. Again, if I'm to believe this graph, more context would help.
   4. No consideration of other factors that might lead to changes in public concern?
   5. No consideration of factors that might lead to *both* an increase in coverage *and* an increase in concern?

I'm sure I could come up with 5 more reasons to doubt this graph if I thought for another 60 seconds...

I'd expect these series to be cointegrated. A chart or OLS isn't going to prove chicken or egg.

Why is it telling? That's true for everything the media covers.

> That's true for everything the media covers.

You believe this. (I also tend to believe it.) But why do we believe it? Are we basing that belief on data? Or on conjecture?

This chart is the first one I've seen that starkly lays out an argument based on data that this effect exists.

You don't need data to know something. Sometimes, data helps.

Indeed. I can plainly know that the Earth is flat just by looking out the window.

It's not news, it's the Daily Mail.

What a great update, thanks for posting!

The economist is a fantastic benchmark when it comes to data visualisation. One thing to note is they publish a lot of the underlying data and models behind their visualisations on their github. If you know R it's a tremendous resource.

https://github.com/TheEconomist

"dual axis charts can often be a great choice."

I generally find that a second Y axis creeping in is perhaps an indicator to stop and have a really deep think about what you are trying to achieve. You might try doing a 3D graph for example where x, y1, y2 becomes x, y, z then spin and explore. However you have to remember that y1 and y2 are both dependent on x (by definition) so when you put y2 to a separate dimension, it is not independent from y1 (or is it?)

There are no hard and fast rules when it comes to spin doctoring via graphs, and as the old adage doesn't go: There are liars, damned liars and politicians.

The only one that's improved is the one from Brazil, to be honest. The rest is taste.

Besides, it's ok if the graph takes a bit to digest, other wise you can just keep printing the same three graphs over and over merely renaming the axis.

This is a pretty good article and for the most part, should be heeded. It's quite rare for the audience of a chart to exclusively be highly-numerate people (and these people, who are often inundated with data, are not immune from being misled by poorly-conceived charts). It's kind of strange that the top-voted comment points to "better" advice while also directly contradicting the article's main point ("dual axis charts can often be a great choice").

I mean, certainly you have the right to add some color but it comes off like you are saying to ignore the article entirely in favor of your alternatives.

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