Creating streamline plot on plotly for longitude/latitude points

Question

I want to plot the ocean currents data using plotly, I have the following information:

longitude (array | shape -> (360,)): The array with longitude points
latitude (array | shape -> (140,)): The array with latitude points
U (2d-array | shape -> (140, 360)) : The array with x-component of current velocities
V (2d-array | shape -> (140, 360)) : The array with y-component of current velocities

I tried it with matplot and it works well:

    ax = plt.axes(projection=ccrs.PlateCarree())
    ax.coastlines()
    mymap=plt.streamplot(lon, lat, U, V, density=6, transform=ccrs.PlateCarree(), color=U, cmap='autumn')
    ax.plot(xx, yy)

    plt.show()

But plotly throws the following error:

    fig = ff.create_streamline(lon, lat, U.T, V.T)
    File "C:\Users\91983\anaconda3\envs\face\lib\site-packages\plotly\figure_factory\_streamline.py", line 112, in create_streamline
    utils.validate_equal_length(x, y)
    File "C:\Users\91983\anaconda3\envs\face\lib\site-packages\plotly\figure_factory\utils.py", line 99, in validate_equal_length    raise exceptions.PlotlyError(
    _plotly_utils.exceptions.PlotlyError: Oops! Your data lists or ndarrays should be the same length.

I tried

    x, y = np.meshgrid(lon, lat)
    x, y = np.vstack([x.ravel(), y.ravel()])

But I am unable to appropriately modify U and V

Example data:

lon = [-9.5, -8.5, -7.5, -6.5, -5.5]
lat = [-10.5, -11.5, -12.5]
U = [[ 0.01359653 -0.06777997 -0.01459221], [ 0.10778577 -0.0182181  -0.04552014], [-0.12153802 -0.10809003 -0.08621038], [-0.03212119  0.03420004  0.0011446 ], [0.01677546 0.02874723 0.121696  ]]
V = [[-0.0171657  -0.06966873 -0.05578572 -0.03955243 -0.05238442], [-0.01327003 -0.02819919 -0.07014654 -0.06515452 -0.00050288], [-0.01017548 -0.01393307 -0.03817951 -0.03380885  0.03111682]]

user_4407613 · Answer

TL;DR

error is caused due to length(longitude) != length(latitude)

as rightly pointed out by CAPSLOCK.

Here it is code.

first line of create_streamline

   utils.validate_equal_length(x, y)
   utils.validate_equal_length(u, v)

which is comparing length of x and y, u and v. here is code

length = len(args[0])
if any(len(lst) != length for lst in args):
    raise exceptions.PlotlyError(
        "Oops! Your data lists or ndarrays " "should be the same length."
    )

Creating streamline plot on plotly for longitude/latitude points

1 Answers

TL;DR

error is caused due to length(longitude) != length(latitude)

this means assumption of plotly in code is equal length x and y axis.

Your case is special case (unequal length x and y axis) for which is as of now not supported in plotly yet.