Name

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    HIST_ND_ADAPTIVE

Purpose

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    Given a list of particle positions (and optional particle weights), bin sizes, and ranges,
    creates a density image where the regions with fewer particles are sampled at larger bin sizes.
    This can be used as a drop-in for HIST_ND_WEIGHT, but it divides by the bin area (or ND-volume).

Category

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    Plot

Calling Sequence

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    Result = HIST_ND_ADAPTIVE(V, Bin)

Inputs

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    V: An NDxN element array of the ND-dimensional positions of the N particles.
    Bin: Size of highest-resolution pixels in output image.

Keyword Parameters

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    MIN: ND-element array of minimum positions in final map. If a scalar, used for all dimensions.
              Default is the minimum particle position in each dimension.
    MAX: ND-element array of maximum positions in final map. If a scalar, used for all dimensions.
              Default is the maximum particle position in each dimension.
    WEIGHT: Array of weights for each particle.
    LEVELMAX: Maximum number of lower-density levels to use (0=no smoothing). Default: 4.
    NTHRESHOLD: Minimum number of particles within a pixel before going to the next level. Default: 3.

Outputs

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    Result contains a density map of the points. The map has its highest effective
    resolution in the regions with the most points, but degrades to factor-of-2 lower resolutions
    when the number of particles per pixel drops below the threshold.

Example

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    n = 100000
    positions = 5*randomn(seed, 2, n)
    image = hist_nd(positions, 0.5, min=-20, max=20) * 4
    smthimage = hist_nd_adaptive(positions, 0.5, min=-20, max=20)
    isurface, image, zrange=[0,3], title='Original'
    isurface, smthimage, zrange=[0,3], title='Smooth'

Modification History

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    Written by: Jeremy Bailin 20 June 2011