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Categorical choropleths with legends #3468
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That's correct.
choroplethdon't support legend items.You can shrink down the colorbars (one for each trace) to do something like:
- set the color directly, like with
marker.color, instead of doing a dance withzandcolorscale
So, you want
z(that should have been calledvalue, by the way) andmarker.colorto do the exact same thing? I can't say I'm a fan. It would be weird (to me) to have a "primary" data array (i.e. you need it to see stuff) stuck insidermarker.So that I could easily switch between
choroplethandscattergeolike with this one:By a similar argument, should we rename the
piedata arraysxandyso that we can easily switch frombar<-->pie? I doubt it.Now, I'm not saying we shouldn't try to make trace-to-trace correspondences easier. This has been discussed during previous work on
relayout. The last item of #2025 is:add a way to declare correspondence between attributes of different name across trace types (e.g. to generalize type edits involving pie traces, scattergeo lon/lat should correspond to x/y, ...)
Maybe we can find a way to declare those correspondence in the plot-schema. Thoughts?
- set the color directly, like with
X and Y are terrible attribute names for pie, in just the same way as Z is a much worse attribute name than color for controlling the color of a choropleth marker, so no, obviously I would not favour those for pie!
However, since you bring it up, pie’s label/value would be a great fit for bar, since they would not require transposition to swap orientation, as x and y currently do.
Straw man aside: yes I would favour grandfathering in z as a legacy way of specifying marker.color if we added it to choropleth.
The problem with playing discretization tricks with the colorbar is that it doesn’t have the same behaviour as the legend with respect to clicking to hide etc, so it’s inconsistent with the rest of the traces. This is a problem with parcats, parcoords etc as well.
Maybe we can find a way to declare those correspondence in the plot-schema.
So this ⏫ isn't good enough?
My main goal is to be able to specify the color of the country directly like we can specify the color of a marker in scatterX. Z doesn’t permit this atm, so no, declaring a correspondence doesn’t help :)
Conversely, allowing CSS color names in an array called Z seems awkward.
We could make
zaccept color names (and omitcolorscale).We could, yes. And we could allow traces to be added to the legend. That would indeed allow me to make the figures I want.
Thinking about this again maybe
marker.colorfor color names + legend items would be best.That way, user that inputs
zgets a colorscale and a colorbar, user that inputsmarker.colorgets a legend item. There wouldn't be anymarker.colorscaleandmarker.coloritems couldn't be numeric (not a true "data" array, that makes me 😄 ). It will bearrayOkthough.Heh ok that might work also. OTOH I could also see an argument that a true choropleth by definition expresses continuous values and that we should have a new trace type called indicatormap or something that accepts only categorical colors.
Also: choropleth has a “showlegend” attribute atm that doesn’t do anything, which initially led me down this path ;)
Right, all traces have a
showlegendattribute even though some (or most?) of them don't support legendsRelated:
For reference, BTW, this is the kind of figure I'm aiming at:
Reacted by etpinard, av3wagner and John AsbaghiJust to drill in a bit on the
zvsmarker.colorthing... @etpinard you saidIt would be weird (to me) to have a "primary" data array (i.e. you need it to see stuff) stuck insider marker.
OK, but how is this different from something like
scattergeo? If you omitmarker.colorthen all the markers are the same default color. We could do the same thing forchoroplethsuch that if you only pass inlocationthen all the countries (or whatever) are the same color. That's not a useless thing: as an indicator map, it's like "here are all the places where X".I think it would be quite weird to have
choroplethbe the one trace wheremarker.coloraccepts only colors and not continuous values.8 remaining items
I think attributes which control color should be called
colorI'd argue that
zfor choropleth is more than just color, it's a primary data array. A choropleth trace w/o azdoesn't show anything. A scattergeo trace w/omarker.colorstill shows points.As I said above re choropleth traces without
z:OK, but how is this different from something like scattergeo? If you omit marker.color then all the markers are the same default color. We could do the same thing for choropleth such that if you only pass in location then all the countries (or whatever) are the same color. That's not a useless thing: as an indicator map, it's like "here are all the places where X".
- Reacted by MH Manuel Haqiqatkhah, JP Cassil, Adam H. Sparks, Nicolas Kruchten, Mojtaba Samimi, Illia Kachko, Brian Moore, Marco Aurélio Guerra Pereira, Laurențiu Leahu-Vlăducu and Kenneth BurchfielReacted by Mojtaba Samimi, abshaw2 and Marco Aurélio Guerra Pereira
It looks like px.choropleth z field still does not support categorical legend items? I'm not sure where this discussion ended, but at present setting z to a categorical series simply produces a blank map. Thanks!
That’s right, z still supports only continuous color but you can now add multiple single-color choropleth traces with legend items to get the same effect. See https://plot.ly/python/choropleth-maps/ for an example with Plotly Express in Python.
Hi! Thanks for getting back to me. Which section should I be looking at? The figure under "Discrete Colors" is essentially what I am aiming to create. However, the example code provided no longer runs.
It definitely runs but it requires version 4.5.0 of Plotly.py which came out a couple of weeks ago.
That’s right, z still supports only continuous color but you can now add multiple single-color choropleth traces with legend items to get the same effect. See https://plot.ly/python/choropleth-maps/ for an example with Plotly Express in Python.
Hi, I want to know how to reorder the legeng items. Because sometimes these legends may have order meaning, for example bins, 1-10, 1-20, 21-30...
Legend order depends on trace order in the
dataarray.@nicolaskruchten I saw that this topic was closed and included in #4386 but I still don't understand how to achieve a categorical choropleth using the documentation . My data is a Pandas DataFrame with two columns: the country name and the cluster it belongs in. I want to color the world map based on the cluster of each country - very similar to your examples. I had tried coloring a map by cluster in the past and this is as close as I was able to get using plotly.graph_objects. The issue with this is that the legend was still a continuous color scale, not a list of categories(i.e. cluster labels).
This is example in the Plotly documentation is the closest to what I'm trying to achieve but my data is not in geojson format. Would appreciate any advice. Thank you!@ahertel if you're looking for information on how to do this in Python I would recommend opening an issue in the Plotly.py repo, but for completeness, here's a PX example without GeoJSON for categorically-coloring statewise choropleths... it's basically the same as the one here https://plotly.com/python/choropleth-maps/#using-builtin-country-and-state-geometries but with categorical instead of continuous color:
import plotly.express as px fig = px.choropleth(locations=["CA", "TX", "NY", "AK"], color=["yes", "no", "yes", "no"], scope="usa", locationmode="USA-states") fig.show()
@nicolaskruchten Ah right, I forgot this was the JS page. Thank you so much for responding so quickly and taking the time to write the example code! It worked and it's so much simpler than all the stuff I was playing around with. Here's the result.
Right now it doesn't seem like we can make a categorical choropleth by adding multiple traces with the same color and having legend items appear for them: https://codepen.io/nicolaskruchten/pen/MLwyOZ?editors=0010
Ideally I'd want to be able to:
marker.color, instead of doing a dance withzandcolorscaleSo that I could easily switch between
choroplethandscattergeolike with this one: https://codepen.io/nicolaskruchten/pen/QYbNax?editors=0010