better support for lines on maps in Plotly Express

[nicolaskruchten]

Today, px.line_mapbox and px.line_geo expect rows which are points, which are then split into groups and connected by lines.

In most GIS formats, however, as wrapped by GeoPandas, the entire line feature is often stored in a single row, just like choropleth geometries. We should have either a new pair of PX functions for this (px.line_feature_mapbox?) or an option to the existing functions (px.line_mapbox(geojson=<geojson>)) to support this option out of the box.

[nicolaskruchten]

See also plotly/plotly_express#29

[harisbal]

This will be a game changing enhancement since it will make plotly a viable alternative for representing geospatial data instead of GIS software.
In addition I would like to suggest the following:
People working with geospatial data are very used to be able to control the width, apart form the color of the line.
I suppose this can be achieved already by iterating over each line and adjusting its width. However, straightforwardly providing this capability in px would be very useful.
Cheers

[nicolaskruchten]

Thanks for the enthusiasm @harisbal! What would you see the function signature looking like in this case? I hesitate a bit about making px.line_mapbox have in effect different "modes" but maybe this is the right way forward.

[nicolaskruchten]

People working with geospatial data are very used to be able to control the width, apart form the color of the line.

Yes, this is indeed a limitation we have right now... we don't provide fine-grained control over width and color per segment, but per line we could.

[nicolaskruchten]

@alexcjohnson what's your instinct on something like this? a new PX function or a new geojson argument that in this case wouldn't map straight down to a trace-level geojson schema attribute? this new argument would be parsed similarly to the iterative approach in the docs here: https://plotly.com/python/lines-on-mapbox/#lines-on-mapbox-maps-from-geopandas

[alexcjohnson]

@nicolaskruchten Feels like various other of the args to px.line_mapbox wouldn't make sense with this kind of input data, and if that's the case then perhaps a new function is a cleaner solution.

[nicolaskruchten]

Actually all the other args except lat/Lon/line_group would work! Color, line_width, eventually facet etc

[alexcjohnson]

Oh OK, I thought it seemed like the data structure would be fairly different so wouldn't support other args the same way - but if it does, then great, just overload the same function!

[harisbal]

Thanks for the enthusiasm @harisbal! What would you see the function signature looking like in this case? I hesitate a bit about making px.line_mapbox have in effect different "modes" but maybe this is the right way forward.

I believe that a mode argument would be very useful here. The two possible modes would be either points or linestrings.
In addition, I feel that for the points case a line_order argument should be also introduced to specify the order of the points.

So in case someone has data as points:

• px.line_mapbox(df, mode='points', lat='lat, lon='lon', line_group='country', line_order='order')

And in case someone has a geodataframe with linestrings:

• px.line_mapbox(dfg, mode='linestrings', linestrings=dfg.geometry)

I'd be glad to help if required. Cheers

[EsbernJakobsen]

Just wanted to give this a bump!

Out-of-the-box support for shapely/GeoPandas LineStrings would be fantastic. I'm aware you've added some support for Shapely Points and Polygons. The GeoPandas support example given in Lines on Maps is useful but it doesn't really exploit the strengths of pandas, as it involves unpacking the dataframe using a loop.

Thanks for all the work so far though! 🙂

[ibhalin]

I'm bumping too. It would be fantastic !

[beajifu]

I want to ask if there is any progress for this feature, because it sounds really good to have support for LineStrings to easily plot a GeoPandas Dataframe. I would appreciate it.