Improved peak location

  • Second derivative of the data is used over the first derivative as the peak locations are easier to locate via Python using a cut off.

  • Location of local peaks of Cd at 06.50mm found using for loop and weighted average:
    peaklocated.png

  • Location of local peaks of Cd at 06.50mm found using for loop and weighted average after processing with median filter:
    peaklocatedmfilter.png

  • text.txt: Code for peak finders and width
Improved Gaussian Fits

  • Gaussian function used:
\begin{equation} f(x) = a e^{- \frac{(x - \mu )^2}{2 \sigma ^2}} + b \end{equation}

  • Where a is amplitude, μ is pixel position, σ is peak width and b is background level.
  • First guess parameters for each peak (obtained from peak finding code) are passed to scipy.optimize.curvefit whose function is defined above. curve_fit returns the optimal parameters which are then passed again to the Gaussian function and the outputs are plotted as fits to the data.

  • Improved Gaussian fits to the Cadmium 6.50mm spectrum peaks:
    Improved_Cd_0650_Gaussians.png
  • Currently x range is limited to ± 50 pixels of the estimated pixel position, in order for the fit to be able to work
  • Still struggles with closely grouped peaks

-- JamesAngthopo - 27 Oct 2016
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Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng Improved_Cd_0650_Gaussians.png r1 manage 40.1 K 27 Oct 2016 - 20:18 WilliamBurrows Improved Gaussian fits to the Cadmium 6.50mm spectrum peaks
Texttxt gaussian_fit.py.txt r1 manage 4.7 K 27 Oct 2016 - 21:50 WilliamBurrows Improved Gaussian fit python code
PNGpng peaklocated.png r1 manage 66.5 K 27 Oct 2016 - 17:42 JamesAngthopo Location of local peaks found using for loop and weighted average
PNGpng peaklocatedmfilter.png r1 manage 64.1 K 27 Oct 2016 - 17:42 JamesAngthopo Location of local peaks found using for loop and weighted average where the data has been filtered using median filter
Texttxt text.txt r1 manage 3.7 K 28 Oct 2016 - 12:39 JamesAngthopo Code for peak finders and width
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Topic revision: r4 - 04 Nov 2016 - WilliamBurrows

 
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