How to set Geoviews map extent programmatically in Panel dashboard

Next problem.

When I have the selection below and click run nothing happens on the map.

But I get an error in the terminal.


Ahh. Ok. So you want me to first draw some boxes using the Box Edit Tool.

Ahh. Ok. So I need to double click in order for the Box Edit Tool to work. That took some time to figure out :slight_smile:

Ahh. I should enable getting better error messages. Seeing the stack trace.

After all that I still get errors.

I would need some more specific guidance on the precise steps I need to take in order to help.

And I would like to help. Because I think your dashboard could be really, really great. And I could learn something from it. And others could as well.

Just a hint if you only have one file of sample_data you will not be able to select anything.

I have more than one file locally but yes, that’s kind of annoying. What I’d really like to do is have the value of the param.FileSelector() set when it reads the list of files. It just seems to populate the widget’s label/display with the filename but the value of the widget remains null. But that’s off topic for this thread.

@Marc Hmmm, unfortunately I’m not sure what’s going on there. It seems that there’s a problem with the field you set as the ID field – I’ll deal with that separately, thanks for pointing it out. When I set the fields like so it seems to work. What happens when you try this?

Input File: ebird_10000.csv
X Field: lng
Y Field: lat
ID field: comName

And then draw boxes. For the BoxEdit tool you can hold shift + drag your mouse on the map to draw a box, or you can double click as per

I’ve been drawing boxes on the coastlines of the Yucatan in Eastern Mexico, and on the coastlines of the Baja peninsula in the West. It seems to work well.

This is unrelated to my extents problem, but since you seem to like the idea of this dashboard (thank you, by the way :slightly_smiling_face:) if you switch tabs above the map after you get results you will see a summary table which describes which birds were found in which boxes; you can sort the columns by clicking them. In this summary table, the values of the ‘identifier’ column come from the field the user selects as the ID field; in the example below I have used comName which displays the common name of the birds. The idea is that users can use whichever data they like, query it by drawing boxes, and find out which data values (identifiers) are in which locations.

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But in my version there are no green dots. Should they be draw initially after having selected the Input File. Or only after having clicked Run?

Ok. After having drawn some boxes and clicked the Run button I see some green dots. And also the chart resets the zoom

But in my version there are no green dots. Should they be draw initially after having selected the Input File. Or only after having clicked Run?

As you’ve discovered, the green dots only appear after configuring (select input file, selecting fields, drawing boxes) and pushing ‘Run’. Thanks for you persistence!

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Would you not want the dots to show up initially? (After having selected a file?)

@Marc Can you clarify what you mean by this? When I switch to the chart tab, sort fields, switch back to the map, the map zoom seems unchanged. Does switching to the chart and back to the map change the map extent for you?

What I mean is that when I load the application. And even after having selected in the drop down boxes it looks like

I.e. no green dots.

I would expect there to be some green dots that I then would like to draw boxes around. How do you determine where to draw boxes without the green dots?

Would you not want the dots to show up initially? (After having selected a file?)

No, I only want the dots to appear after hitting the Run button. As it is now the functionality is incomplete compared to my full set of requirements. In a later version the inputs will be a combination of local files provided by the user and/or a REST services which will be queried when ‘Run’ is pushed. The services I will query contain A LOT of data so I don’t want to try to retrieve it and plot it. This dashboard will also serve the purpose of querying the various data sources.

I would expect there to be some green dots that I then would like to draw boxes around. How do you determine where to draw boxes without the green dots?

When this dashboard is complete it will query some REST services which have data with global distribution; the current local ebird data in Mexico is just for testing. When connected to the REST services it would be impractical to download hundreds of millions (sometimes billions) of rows of data to plot on the map before the user even draws their boxes. So in the final version the user can draw boxes anywhere they want; if there’s no data within a box that’s fine.

In this version I attempt to use .options(xlim,ylim) on the overlay to set the map extent e, which is a param.Parameter() after the ‘Run’ button is pressed.

This version doesn’t exactly work but I don’t know why. The properties of the map are set correctly but only work on a new instance of the map inline in the Jupyter Notebook. In the dashboard it results in the map being reprojected and the drawn boxes vanishing. I’m stumped as to why the hv.streams.BoxEdit data is removed from the map.

You will see that my code to set the extents of the map has works correctly, but is not reflected in the dashboard for some reason. It is only reflected in a new instance of the map. And while the map in the dashboard is skewed (reprojected?) the new inline map in the notebook is not.

import panel as pn
import param
import geoviews as gv
import holoviews as hv
import pandas as pd
import geopandas as gpd
from cartopy import crs
from datashader.utils import lnglat_to_meters
from shapely.geometry import Point, box


class Inputs(param.Parameterized):

input_file = param.FileSelector(path='.\jupyter-geo-box-query\sample_data\*.csv', doc='A .csv file selector for input data')
x_field    = param.Selector(doc='A field selector for longitude')
y_field    = param.Selector(doc='A field selector for latitude')
id_field   = param.Selector(doc='A field selector for the identifier')
data       = None

@param.depends('input_file', watch=True)
def update_inputs(self):
    df                          = pd.read_csv(self.input_file)
    numeric_cols                = list(df.select_dtypes(include=['float64']).columns)
    columns                     = [x for i,x in enumerate(df.columns) if x !='Unnamed: 0']
    self.param.x_field.objects  = numeric_cols
    self.x_field                = numeric_cols[0]
    self.param.y_field.objects  = numeric_cols
    self.x_field                = numeric_cols[0]
    self.param.id_field.objects = columns
    self.id_field               = columns[0]                   = df

class Mapview(param.Parameterized):

opts          = dict(width=1200,height=750,xaxis=None,yaxis=None,show_grid=False)
tiles         = gv.tile_sources.CartoEco().apply.opts(**opts)
box_polygons  = gv.Polygons([]).opts(fill_alpha=0.1)
box_colours   = ['red','blue','green','orange','purple']
box_stream    = hv.streams.BoxEdit(source=box_polygons, num_objects=5, styles={'fill_color': box_colours})
template_df   = pd.DataFrame({'x_meters': [], 'y_meters': []}, columns=['x_meters', 'y_meters'])
dfstream      = hv.streams.Buffer(template_df, index=False, length=10000)
points        = hv.DynamicMap(hv.Points, streams=[dfstream]).opts(
                              size=5, color='green', fill_alpha=0.3, line_alpha=0.4)
e             = param.Parameter(default=[None,None,None,None],precedence=-1)

def show_map(self):
    print('show_map() has been called.')
        if self.e[0] is None:
            print('Using global extent')
            return (self.tiles * self.box_polygons * self.points).options(xlim=(-20000000,20000000),ylim=(-6000000,6000000))
            print(f'Using new extents: {self.e[0]},{self.e[2]},{self.e[1]},{self.e[3]}')
            return (self.tiles * self.box_polygons * self.points).options(xlim=(self.e[0],self.e[2]),ylim=(self.e[1],self.e[3]))            
        print('Problem in show_map()')

class Dashboard(param.Parameterized):

input1    = Inputs()
input2    = Inputs()
input3    = Inputs()
input4    = Inputs()
input5    = Inputs()
mapview   = Mapview()

button = param.Action(lambda x: x.param.trigger('button'), label='Run')

def project_to_meters(self, df, x, y):
        df.loc[:,'x_meters'], df.loc[:,'y_meters'] = lnglat_to_meters(df[x],df[y])
        geometry = [Point(xy) for xy in zip(df.x_meters, df.y_meters)]
        web_merc = {'init': 'epsg:3857'}
        return gpd.GeoDataFrame(df, crs=web_merc, geometry=geometry)
        print("""Could not project specified coordinate fields to meters. Make sure the X Field and Y Field 
              values have been set correctly.\n""")

def convert_box_stream_data_to_geometry(self):
        box_data =        
            num_boxes = len(box_data['x0'])
            num_boxes = 0

        boxes     = []
        for i in range(0,num_boxes):
            x0 = box_data['x0'][i]
            y0 = box_data['y0'][i]
            x1 = box_data['x1'][i]
            y1 = box_data['y1'][i]
        if len(boxes)>0:
            return boxes
        print('Could not convert boxes drawn on map into geometries.\n')

def run_analysis(self):
        # clear previous results

        # Convert each input into a GeoDataFrame and project coordinates to meters
        datasets  = []
        id_fields = []
        for i in [self.input1, self.input2, self.input3, self.input4, self.input5]:
            if isinstance(, pd.core.frame.DataFrame):
                gdf = self.project_to_meters(, i.x_field, i.y_field)

        # Convert boxes drawn on the map into Shapely geometries
        if len(datasets)>0:
            boxes     = []
            box_data =
            for i in range(0,len(box_data['x0'])):
                x0 = box_data['x0'][i]
                y0 = box_data['y0'][i]
                x1 = box_data['x1'][i]
                y1 = box_data['y1'][i]

            # Do intersections of each box on each GeoDataFrame & send results to the map
            df_all_boxes = pd.DataFrame()
            df_final = pd.DataFrame()
            box_labels = []
            for i in range(0,len(datasets)):
                for b in boxes:
                    box_label = self.mapview.box_colours[boxes.index(b)] + '_box'
                    datasets[i][box_label] = datasets[i].intersects(b)
                    selected = datasets[i].loc[datasets[i][box_label]==True].drop(columns='geometry')
                    df_all_boxes = pd.concat([df_all_boxes,selected[['identifier',box_label]]],axis=0,ignore_index=True)

            for ident in pd.unique(df_all_boxes['identifier']):
                dfx = df_all_boxes.loc[df_all_boxes['identifier']==ident]
                box_values = {'identifier':[ident]}
                for bl in box_labels:
                    # returns true if any of the values are true
                    # else returns false
                    box_values[bl] = [dfx[bl].any()]
                df_ident = pd.DataFrame.from_dict(box_values)
                df_final = pd.concat([df_final, df_ident],axis=0)

            def summarize_boxes(row):
                cols = list(row.axes[0])
                s = []
                for c in cols:
                    if 'box' in c:
                        if row.values[cols.index(c)]:
                return ','.join(s)

            summary = df_final.copy()
                # build an extent to zoom to based on the current drawn boxes
                boxes =
                xmin = min(boxes['x0'])
                xmax = max(boxes['x1'])
                ymin = min(boxes['y0'])
                ymax = max(boxes['y1'])
                new_extent = box(xmin,ymin,xmax,ymax)
                self.mapview.e = new_extent.bounds
                print('Problem calculating new map extent.')
                summary['Found_In'] = summary.apply(lambda row: summarize_boxes(row),axis=1)
                return pn.widgets.DataFrame(summary, disabled=True, fit_columns=True, width=700)
                print('There was an error creating the final output summary table.\n')
            print('You must select at least one input dataset.\n')
        print('Something went wrong in the run_analysis() function.\n')
        return('Something went wrong in the run_analysis() function.')

def view(self):
    desc = """This is a demonstration dashboard with incomplete functionality. Its purpose
    is to sit here and look pretty. We can put graphics and stuff in here to
    make it look all fancy."""

    logo = '.\images\logo_panel_stacked_s.png'
    button_desc = """The <i>Run</i> button will execute the spatial intersection and generate
    a table of identifiers found within each box and in multiple boxes.<br><br>
    Push the <i>Run</i> button after configuring all inputs and drawing boxes on the map."""

    return pn.Row(
                '## Description',
                '### Configure Inputs',
                    ('Input 1',self.input1),
                    ('Input 2',self.input2),
                    ('Input 3',self.input3),
                    ('Input 4',self.input4),
                    ('Input 5',self.input5)),
                ('Map View', pn.Column(self.mapview.show_map())),
                ('Results Table', self.run_analysis)))

d = Dashboard()

After you run this notebook, select a file and fields and draw boxes in the dashboard and hit ‘Run’. Look at the map. Then switch to the notebook and run this in a new cell at the bottom:


Result in dashboard:

You can see that:

  • the map extents were reset to the initial extent
  • the map has been skewed (projection has changed?)
  • the green dots are there
  • the drawn boxes are there

Result in new inline map in the notebook:

You can see that:

  • the map extents were set correctly to match the extents of the drawn boxes
  • the map has not been skewed or reprojected
  • the green dots are there
  • the drawn boxes are not there

I’m confused by the differing properties of these two maps and don’t understand why they are different because they are produced by the same code.

I found this in the Holoviews FAQ so I set clone=False in my Mapview.show_map() method but the dashboard map still does not zoom to the extent I specify with xlim & ylim, but a new instance of the map/overlay does.

Q: Why are my .options(), .relabel(), .redim(), and similar settings not having any effect?

A: By default, HoloViews object methods like .options and .redim return a copy of your object, rather than modifying your original object. In HoloViews, making a copy of the object is cheap, because only the metadata is copied, not the data, and returning a copy makes it simple to work with a variety of differently customized versions of any given object. You can use .opts() or pass clone=False to .options() if you wish to modify the object in place, or you can just reassign the new object to the old name (as in e = e.relabel("New Label")

    def show_map(self):
            gv.opts.Points(size=5, color='green', fill_alpha=0.3, line_alpha=0.4),
        if self.e is None:
            print('Using global extent')
            return self.map_layout
            print(f'Using new extents: {self.e[0]},{self.e[2]},{self.e[1]},{self.e[3]}')
            return self.map_layout.options(xlim=(self.e[0],self.e[2]),ylim=(self.e[1],self.e[3]),clone=False)

This version of my notebook is attached here.

Fix Extents --Options(xlim, ylim).ipynb (12.3 KB)

I’m starting to think that what I am trying to do is not currently possible and that I should submit a ticket to expose this functionality instead of pursuing this question here.

Ok, here’s a simpler example and a simpler question to try to get some clarity on this. @Marc @philippjfr I would very much appreciate your thoughts. I’ve stripped this down to a much simpler example without Panel or Param or any of my classes. Running the first cell gives me this map plot.

Then I can zoom the map & draw boxes using BoxEdit.

So far, so good. But when I run the last cell to send data to the map via hv.streams.Buffer() the map extents reset and the boxes I drew disappear.


I want to prevent the map from resetting and I want to prevent the boxes from disappearing. Can I do this?

The code and sample file for the points are here.

ebird_10000.csv (1.5 MB)

Map Reset Issue.ipynb (1.6 KB)

import geoviews as gv
import holoviews as hv
import pandas as pd


tiles         = gv.tile_sources.CartoEco()

box_polygons  = gv.Polygons([])
box_colours   = ['red','blue','green','orange','purple']
box_stream    = hv.streams.BoxEdit(source=box_polygons, num_objects=5, styles={'fill_color': box_colours})

template_df   = pd.DataFrame({'lng': [], 'lat': []}, columns=['lng', 'lat'])
dfstream      = hv.streams.Buffer(template_df, index=False, length=10000)
points        = hv.DynamicMap(gv.Points, streams=[dfstream])

df = pd.read_csv('.\sample_data\ebird_10000.csv')

tiles.opts(global_extent=True,width=750,height=400) * box_polygons * points.opts(data_aspect=1)

And the last cell:

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Is there a bug with hv.streams.Buffer() which causes the map plot to reset extents? Is that expected behaviour? When I used hv.streams.Pipe() instead of .Buffer() the map does not reset. However, I can’t use .Pipe() as my solution because the hv.streams.Pipe.clear() method doesn’t seem to work, while calling hv.streams.Buffer.clear() does work. Is there a bug with hv.streams.Pipe.clear()?

From that when using the Buffer stream the view will always follow the current range of the data by default, by setting buffer.following=False or passing following as an argument to the constructor this behavior may be disabled.

I don’t think this is working properly when the hv.streams.Buffer() is used with Geoviews. When I set following=False it is true that the map extents don’t reset but the overlay does not maintain the correct aspect ratio for the x & y axes so that the plot ends up looking like this even though I set data_aspect=1.

Hi @dr_clank.

I have been hoping to get back but have a lot of work. Maybe on the weekend. I hope other Geoviews/ Panel users would chime in. Your use case looks really awesome.

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Wow. I think I fixed it.

So creating my plot by setting data_aspect=0.5 seems to do the trick since the range of longitudes is -/+180 while the range of latitudes is -/+90 (i.e. y:x ratio of 0.5)

(tiles * box_polygons * points).opts(data_aspect=0.5)