Holoviews gridded dataset example - how to create dataset from 2D image (numpy array)

Question

I am trying to create a holoviews dataset from a 2D image stored as a numpy array. Holoviews provides a fairly comrehensive guide for gridded data sets here: http://holoviews.org/getting_started/Gridded_Datasets.html

In the example linked above they create a dataset from a 3D numpy array (time, x, y) as follows:

ds = hv.Dataset((np.arange(50), np.arange(111), np.arange(62), calcium_array), kdims=['Time', 'x', 'y'], vdims=['Fluorescence']) ds

where calcium_array is a numpy array with shape (50,11,62). This works fine for me running Python 3.6, And holoviews version 1.8.4-x-gde78cf33a

When I try to modify the example for a simple 2D image like so

ds = hv.Dataset((np.arange(111), np.arange(62), calcium_array[0,:,:]), kdims=[ 'x', 'y'], vdims=['Fluorescence']) ds

I get the exception ValueError: None of the available storage backends were able to support the supplied data format.

My modifications to the working example code basically boil down to dropping the first dimension both in the array as well as the kdims. Am I doing something wrong or is this a bug ?

Answer 1

Try:

ds = hv.Dataset((np.arange(50), np.arange(111), np.arange(62), calcium_array),
                kdims=['Time', 'x', 'y'], vdims=['Fluorescence'])
ds

=> :Dataset   [Time,x,y]   (Fluorescence)


ds = hv.Dataset((np.arange(50), np.arange(111), calcium_array[0,:,:]),
                kdims=['x', 'y'], vdims=['Fluorescence'])
ds

=> :Dataset   [x,y]   (Fluorescence)

Maybe we need a better error message.