.. _RST Preprocessing: Preprocessing ============= Rampy offers handful functions to preprocess your spectra. Do not hesitate to propose/ask for new functionalities! Below you will find the documentation of the relevant functions. They are often used in the different example notebooks: :ref:`RST Notebooks` Flip the X axis --------------- Some spectra come with decreasing X values. Rampy offers a simple function to flip them. This can be necessary to e.g. resample them (as interpolation algorithms usually require the X values to increase). The following function does this. It even allows even arbitrary X value positions. It returns a sorted array with an increasing x axis. .. autoclass:: rampy.spectranization.flipsp :members: :undoc-members: :show-inheritance: Shift the X axis ---------------- You can shift the X axis from a given value using the following function: .. autoclass:: rampy.spectranization.shiftsp :members: :undoc-members: :show-inheritance: Extract a portion / portions of a signal ---------------------------------------- You can use the function ``rampy.extract_signal()`` to do that (old version: ``rampy.get_portion_interest``) .. autoclass:: rampy.baseline.extract_signal :members: :undoc-members: :show-inheritance: Remove spikes ------------- Spikes can be removed via the ``rampy.despiking()`` function. It takes as input X and Y values of a spectrum and a threshold. The threshold is the number of standard deviation above the mean noise value that a point must be to be considered as a spike. For instance, if the threshold is 3, then a point will be considered as a spike if it is 3 standard deviation above the mean of the noise. The function will then replace the spike by the mean of *k* points before and after the spike. .. autoclass:: rampy.spectranization.despiking :members: :undoc-members: :show-inheritance: Resampling a spectrum --------------------- We need sometime to resample a spectrum with a new X axis. ``rampy.resample()`` offers such ability. For instance, we have a spectrum that has a X axis from 400 to 1300 cm-1, with points each 0.9 cm-1. We want the same but with an X axis with a value each cm-1. We can do for our spectrum: .. autoclass:: rampy.spectranization.resample :members: :undoc-members: :show-inheritance: Normalisation ------------- Rampy provides the ``rampy.normalisation()`` function to normalise the Y values of a spectrum to - the maximum intensity - the trapezoidal area under the curve - to min-max values of intensities .. autoclass:: rampy.spectranization.normalise :members: :undoc-members: :show-inheritance: Temperature and excitation line effects --------------------------------------- Raman spectra may need correction from temperature and excitation line effects. See the review of `Brooker et al. 1988 `_ for details. rampy offers several way to do so with the ``rampy.tlexcitation()`` function. .. autoclass:: rampy.tlcorrection.tlcorrection :members: :undoc-members: :show-inheritance: Wavelength-wavenumber convertion -------------------------------- The ``convert_x_units()`` function allows to convert your X values in nm in inverse cm, or the opposite! Do not hesitate to propose new ways to enrich it! .. autoclass:: rampy.spectranization.convert_x_units :members: :undoc-members: :show-inheritance: