shotGroups (version 0.2-2)

groupSpread: Spread measures of a single group of bullet holes

Description

Provides spread measures and their graphical representations for a single group of bullet holes.

Usage

groupSpread(xy, plots = TRUE, level = 0.5,
            dstTarget = 25, conversion = 'm2cm')

Arguments

xy

a numerical (n x 2)-matrix with the (x,y)-coordinates of n points (1 row of coordinates per point).

plots

a logical value indicating whether diagrams should be shown.

level

a numerical value giving the coverage for the confidence ellipse.

dstTarget

a numerical value giving the distance to the target in MOA calculation. See getMOA.

conversion

how to convert the measurement unit for distance to target to that of the (x,y)-coordinates in MOA calculation. See getMOA.

Value

• A list with the results from the numerical analyses and statistical tests.
• sdXY
  standard deviations of x- and y coordinates (in original measurement units and MOA).
• CIsdXY
  parametric 95%-confidence interval for the standard deviations of x- and y coordinates (in original measurement units).
• sdXYrob
  robust standard deviations of x- and y-coordinates (in original measurement units and MOA).
• covXY
  covariance matrix of (x,y)-coordinates.
• covXYrob
  robust estimate of covariance matrix of (x,y)-coordinates.
• meanDistToCtr
  average distance from points to their center (in original measurement units and MOA).
• maxPairDist
  maximum pairwise distance between points (center-to-center, a.k.a. maximum spread, in original measurement units and MOA).
• groupRect
  width and height of minimum bounding box (in original measurement units and MOA).
• minCircleRad
  radius for the minimum enclosing circle (in original measurement units and MOA).
• confEll
  length of semi-major and semi-minor axis of the confidence ellipse (in original measurement units and MOA).
• confEllRob
  length of semi-major and semi-minor axis of the confidence ellipse based on a robust estimate for the covariance matrix (in original measurement units and MOA).
• confEllShape
  aspect ratio and flattening of the confidence ellipse.
• confEllShapeRob
  aspect ratio and flattening of the confidence ellipse based on a robust estimate for the covariance matrix.
• CEPrand
  modified RAND R-234 estimate for the circular error probable (CEP, in original measurement units and MOA).

Details

Robust estimate for the covariance matrix of (x,y)-coordinates is from covMcd using the MCD algorithm. In addition to the numerical results listed below, this function produces the following diagrams:

• a scatterplot of the (x,y)-coordinates together with group center, circle with average distance to center, and 100*level\%-confidence ellipse - the latter also based on a robust estimate for the covariance matrix
• a scatterplot of the (x,y)-coordinates together with the minimum bounding box, minimum enclosing circle, and maximum group spread
• a histogram for distances to group center including a nonparametric kernel density estimate

See Also

getDistToCtr, getMaxPairDist, getMinBBox, getMinCircle, getConfEll, getCEP, getMOA, hist, kernel, covMcd,

Examples

xy  <- matrix(round(rnorm(200, 0, 5), 2), ncol=2)
res <- groupSpread(xy, level=0.5, dstTarget=25, conversion='m2cm')
names(res)
res$sdXYrob
res$meanDistToCtr
res$maxPairDist
res$CEPrand