"""
Creates a signal1D from a text file
===================================

This example creates a signal from tabular data imported from a txt file using
:func:`numpy.loadtxt`. The signal axis and the EELS intensity values are
given by the first and second columns, respectively.

The tabular data are taken from https://eelsdb.eu/spectra/la2nio4-structure-of-k2nif4/
"""

import numpy as np
import hyperspy.api as hs

#%%
# Read tabular data from a text file:
x, y = np.loadtxt("La2NiO4_eels.txt", unpack=True)

#%%
# Define the axes of the signal and then create the signal:

axes = [
    # use values from first column to define non-uniform signal axis
    dict(axis=x, name="Energy", units="eV"),
    ]

s = hs.signals.Signal1D(y, axes=axes)

#%%
# Convert the non-uniform axis to a uniform axis, because non-uniform axes do not
# support all functionalities of HyperSpy.
# In this case, the error introduced during conversion to uniform `scale` is negligeable.

s.axes_manager.signal_axes[0].convert_to_uniform_axis()

#%% 
# Set title of the dataset and label for the data axis:
s.metadata.set_item("General.title", "La2NiO4 EELS")
s.metadata.set_item("Signal.quantity", "Intensity (counts)")

#%%
# Plot the dataset:

s.plot()