`to_eV()` function and non-uniform axis

[StePhanino]

Hi everyone, first of all thanks for the lumispy package.

I'm working with CL data, and most of the time I'm playing with interactive ROIs or new hyperspy functions like the hyperspy.api.plot.plot_roi_map() but non-uniform axes are not supported yet.

Would it be reasonable to expand the to_eV() function to include a conversion option like in the following code?

from lumispy.signals import CLSEMSpectrum

n_points = 1024
wl = np.linspace(300,700,n_points)
sigma = 25
wl_center = 500
gaussian = 1/(sigma * np.sqrt(2 * np.pi)) * np.exp( - (wl - wl_center)**2 / (2 * sigma**2))
noise = CLSEMSpectrum(np.random.random((10,10,n_points))/1000)
s = CLSEMSpectrum(np.broadcast_to(gaussian, (10,10,n_points))) + noise

s.axes_manager.signal_axes[0].name = 'Wavelength'
s.axes_manager.signal_axes[0].units = 'nm'
s.axes_manager.signal_axes[0].scale = (700-300)/n_points
s.axes_manager.signal_axes[0].offset = 300

s.axes_manager.navigation_axes[0].name = 'X'
s.axes_manager.navigation_axes[0].units = 'nm'
s.axes_manager.navigation_axes[0].scale = 0.1
s.axes_manager.navigation_axes[0].offset = 100

s.axes_manager.navigation_axes[1].name = 'Y'
s.axes_manager.navigation_axes[1].units = 'nm'
s.axes_manager.navigation_axes[1].scale = 0.1
s.axes_manager.navigation_axes[1].offset = 100

s_ev = s.to_eV(inplace=False)
print(type(s_ev.axes_manager[-1]))

import hyperspy.axes as hsax
old_axis = s_ev.axes_manager[-1].axis
new_axis = hsax.DataAxis(axis=old_axis, name='Energy', units='eV')
new_axis.convert_to_uniform_axis()
print(type(new_axis))
test = s_ev.interpolate_on_axis(new_axis, axis='Energy', inplace=False)
test.plot()

hs.plot.plot_spectra([s_ev.inav[5,5], test.inav[5,5]], legend=['Original data', 'Data after uniform + interpolation'])

fig, ax = plt.subplots()
ax.scatter(old_axis, np.ones(len(old_axis)), label='Non uniform original axis')
ax.scatter(new_axis.axis, 2*np.ones(len(old_axis)), label='Uniform new axis')
fig.legend()

thanks a lot

[jlaehne]

Sorry for the delayed response @StePhanino.

Introducing a uniform_axis option that defaults to False would indeed be a nice option to add now that we have both convert_to_uniform_axis for the axis and interpolate_on_axis for the data available.

Would this be something you could implement @pietsjoh?