Errorbars

[vascotenner]

Is it possible to create plots with errorbars, like plt.errorbar does?

[philippjfr]

This has been one of our main to-do items for a long time now. Now that someone has requested them I don't think there is any excuse not to do them. We'll discuss it today and get back to you.

[jbednar]

Yes, errorbars and stream plots are sorely needed, but note that they can currently be done using the Seaborn interface (see the Seaborn and Pandas tutorial).

[philippjfr]

Just added an ErrorBars Element type. I'll rebuild the Elements tutorial now so there should be an example up on the website fairly soon.

[philippjfr]

The example is now live and can be seen here. Let us know if it works for you and if you need any modifications or have any suggestions. I'll close this issue now.

[jbednar]

Looks good. In the new example, shouldn't it say vertical=False for the second plot? They certainly seem to be horizontal.

I'm not sure that vertical or horizontal is really a plotting option -- isn't this a semantic issue, i.e. declaring that the data is ranging over either x or y? And if so, shouldn't it be a parameter for the Element, not the Element's style options? It doesn't seem like a stylistic choice, to me, but maybe I'm confused.

[philippjfr]

I clearly didn't pay enough attention when implementing it at first but I had already renamed it to horizontal last night. I also wondered what the best way of selecting x-error bars vs. y-error bars was, initially I had separate Elements for each just like we have VLine and HLine. I don't know what the best option is but a parameter on the Element is probably it, any suggestions for naming it?

[jbednar]

Maybe key_index, to specify which key_dimension the error values apply to? By default, key_index=0, indicating that the error bars are for values specified on the x axis, and nearly everyone would use that default (resulting in vertical error bars). But the error bars could apply to any key_dimension in principle, which this proposal would allow.