Rho Parameter

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Figure 1: An azimuthal intensity profile fitted for rho parameter calculation.

The ρ parameter is an orientation parameter, representing the mean mineral particle orientation in bone samples. This plug-in calculates the rho parameter from an azimuthal intensity profile as well as the predominant orientation of the mineral particles. Therefore the profile is fitted by two Gaussian profiles and a baseline. The rho parameter is calculated by dividing the peak area (A1 + A2) by the total area (B + A1 + A2).


  • Peaks: 2 Peaks is the default. Select 4 Peaks if four peaks are visible in the azimuthal profile.
  • 1. Peak Pos.: 0 by default. If not 0, this value is used as start value for fitting the first peak.
  • 2. Peak Pos.: 0 by default. If not 0, this value is used as start value for fitting the second peak.
  • Note: If there are 4 peaks, one should type the first and second peak position in order to fit the peaks better.


  • chi: The chi values of the azimuthal intensity profile.
  • I: The intensity values of the azimuthal intensity profile.
Figure 2: Screenshot of the "Rho Parameter" plugin.
Figure 3: Screenshot of the example Direct Transmission File.


  • chi_shift: For fitting, the azimuthal profile needs to start at a minimum intensity value. Therefore the whole profile gets shifted before fitting. This is the output for the shifted chi values.
  • I_shift: The shifted intensity values.
  • I_fit: The fitted (shifted) azimuthal intensity profile.
  • rho_param: The rho parameter.
  • base_line: The fitted baseline position.
  • peak_area: The area of the peaks (A1 + A2).
  • back_area: The area under the base line (B).
  • fit_param: All fit parameter: [peak(1) position, peak(1) maximum, peak(1) width, peak(2) position, peak(2) maximum, peak(2) width, baseline]