Spectrum Calculation

Table of contents

  1. Introduction
  2. How to use
  3. Behavior
  4. Method
  5. References

Introduction

Spectrum Calculation applies arithmetic to spectral intensities or shifts a spectrum along the wavenumber axis. It can use a constant or another spectrum as the intensity operand, with a preview before applying the same calculation to all spectra.

How to use

  1. Upload data, complete any preprocessing, and open Analytics Page.
  2. Select Spectrum Calculation from Select analytics plot, then choose a target spectrum. Average is the default target.
  3. Choose Y-axis with constant, Y-axis with another spectrum, or X-axis shift.
  4. For a Y-axis calculation, select Add, Subtract, Multiply, or Divide and supply the constant or reference spectrum. For an X-axis shift, select Add or Subtract and enter the shift value.
  5. Review the preview plot. Download its CSV, or click Apply calculation to all spectra to create and download a separate calculated dataset.

Behavior

The preview shows the original target, the reference spectrum when one is used, and the calculated result. Previewing does not change the uploaded or preprocessed session data. Apply calculation to all spectra creates a separate dataframe; its CSV is available alongside the preview CSV.

Constant intensity inputs range from 0 to 1,000,000; a subtraction can still produce negative output intensities. A reference spectrum is combined point by point on the same wavenumber axis, without interpolation. Division by zero is not allowed. An X-axis shift changes wavenumbers but leaves intensities unchanged; shift values may be negative.

Method

For target intensity $I(x)$, constant $c$, and reference intensity $R(x)$, the Y-axis result is $I(x)\mathbin{\circ}c$ or $I(x)\mathbin{\circ}R(x)$, where $\circ$ is addition, subtraction, multiplication, or division. An X-axis shift instead gives $x’=x+\Delta$ or $x’=x-\Delta$ while retaining $I(x)$. Applying the operation to all spectra repeats the chosen operation for each spectrum column and returns a new dataframe.

Parameter Tunable or fixed Implementation
Target spectrum Tunable Average or an individual spectrum; defaults to Average
Calculation type Tunable Y-axis with constant, Y-axis with another spectrum, or X-axis shift
Y-axis operator Tunable Add, Subtract, Multiply, or Divide
Constant value Tunable 0–1,000,000; defaults to 1 for multiplication/division
Reference spectrum Tunable Another available spectrum on the same wavenumber axis
X-axis operator and shift Tunable Add or Subtract a wavenumber shift; default shift 0
Data export Fixed Preview and apply-to-all CSV files use four decimal places

References

  1. SpectraGuru developers. Spectrum calculation implementation.