List of fractals by Hausdorff dimension explained

According to Benoit Mandelbrot, "A fractal is by definition a set for which the Hausdorff-Besicovitch dimension strictly exceeds the topological dimension."Presented here is a list of fractals, ordered by increasing Hausdorff dimension, to illustrate what it means for a fractal to have a low or a high dimension.

Deterministic fractals

Hausdorff dimension
(exact value)
Hausdorff dimension
(approx.)
Name Illustration Remarks
Calculated 0.538 The Feigenbaum attractor (see between arrows) is the set of points generated by successive iterations of the logistic map for the critical parameter value

λinfty=3.570

, where the period doubling is infinite. This dimension is the same for any differentiable and unimodal function.[1]

log32

0.6309 Built by removing the central third at each iteration. Nowhere dense and not a countable set.
-log2
log\left(\displaystyle1-\gamma\right)
2
0<D<1 1D generalized symmetric Cantor set Built by removing the central interval of length

\gammaln-1

from each remaining interval of length

ln-1=(1-\gamma)n-1/2n-1

at the nth iteration.

\gamma=1/3

produces the usual middle-third Cantor set. Varying

\gamma

between 0 and 1 yields any fractal dimension

0<D<1

.[2]

log2\varphi=log2(1+\sqrt{5})-1

0.6942 Built by removing the second quarter at each iteration.[3]

\varphi=(1+\sqrt{5})/2

(golden ratio).

log105=1-log102

0.69897 Similar to the Cantor set.[4]

log(1+\sqrt{2})

0.88137 Spectrum of Fibonacci HamiltonianThe study of the spectrum of the Fibonacci Hamiltonian proves upper and lower bounds for its fractal dimension in the large coupling regime. These bounds show that the spectrum converges to an explicit constant.[5]

1

1 Built by removing the central interval of length

2-2n

from each remaining interval at the nth iteration. Nowhere dense but has a Lebesgue measure of 1/2.

2+log2

1
2

=1

1 Defined on the unit interval by

f(x)=

infty
\sum\nolimits
n=0

2-ns(2nx)

, where

s(x)

is the triangle wave function. Not a fractal under Mandelbrot's definition, because its topological dimension is also

1

.[6] Special case of the Takahi-Landsberg curve:

f(x)=

infty
\sum\nolimits
n=0

wns(2nx)

with

w=1/2

. The Hausdorff dimension equals

2+log2w

for

w

in

\left[1/2,1\right]

. (Hunt cited by Mandelbrot[7]).
Calculated1.0812 Julia set z2 + 1/4 Julia set of f(z) = z2 + 1/4.
Solution

s

of

2

\alpha^ + \alpha^ = 11.0933 Boundary of the Rauzy fractalFractal representation introduced by G.Rauzy of the dynamics associated to the Tribonacci morphism:

1\mapsto12

,

2\mapsto13

and

3\mapsto1

.[8]

\alpha

is one of the conjugated roots of

z3-z2-z-1=0

.

2log73

1.12915 Term used by Mandelbrot (1977). The Gosper island is the limit of the Gosper curve.
Measured (box counting) 1.2 Julia set of f(z) = z2 + i.
3log\varphi
log\left(\displaystyle3+\sqrt{13

{2}\right)}

1.2083 Build from the Fibonacci word. See also the standard Fibonacci word fractal.

\varphi=(1+\sqrt{5})/2

(golden ratio).

\begin{align}&

2log
2\left(\displaystyle\sqrt[3]{27-3\sqrt{78
}+\sqrt[3]}\right),\\ &\text2^x-1=2^\end
1.2108 Boundary of the tame twindragon One of the six 2-rep-tiles in the plane (can be tiled by two copies of itself, of equal size).[9] [10]
1.26 The canonical Hénon map (with parameters a = 1.4 and b = 0.3) has Hausdorff dimension 1.261 ± 0.003. Different parameters yield different dimension values.

log34

1.2619 Three anti-snowflakes arranged in a way that a koch-snowflake forms in between the anti-snowflakes.

log34

1.2619 3 Koch curves form the Koch snowflake or the anti-snowflake.

log34

1.2619 L-system: same as dragon curve with angle = 30°. The Fudgeflake is based on 3 initial segments placed in a triangle.

log34

1.2619 Cantor set in 2 dimensions.

log34

1.2619 2D L-system branch L-Systems branching pattern having 4 new pieces scaled by 1/3. Generating the pattern using statistical instead of exact self-similarity yields the same fractal dimension.
Calculated1.2683 Julia set z2 - 1 Julia set of f(z) = z2 − 1.
1.3057 Starting with 3 tangent circles, repeatedly packing new circles into the complementary interstices. Also the limit set generated by reflections in 4 mutually tangent circles. See [11]
1.328 5 circles inversion fractal The limit set generated by iterated inversions with respect to 5 mutually tangent circles (in red). Also an Apollonian packing. See [12]

log59

1.36521[13] Quadratic von Koch island using the type 1 curve as generatorAlso known as the Minkowski Sausage
Calculated1.3934 Julia set of f(z) = -0.123 + 0.745i

log35

1.4649 Built by exchanging iteratively each square by a cross of 5 squares.

log35

1.4649 Quadratic von Koch curve (type 1)One can recognize the pattern of the Vicsek fractal (above).

log\sqrt{5

} \frac
1.4961 Quadric cross Built by replacing each end segment with a cross segment scaled by a factor of 51/2, consisting of 3 1/3 new segments, as illustrated in the inset.

Images generated with Fractal Generator for ImageJ.

2-log2\sqrt{2}=

3
2
1.5000 a Weierstrass function:

f(x)=

infty
\sum
k=1
\sin(2kx)
\sqrt{2

k

}
The Hausdorff dimension of the graph of the Weierstrass function

f:[0,1]\toR

defined by

f(x)=

infty
\sum\nolimits
k=1

a-k\sin(bkx)

with

1/b<a<1

and

b>1

is

2+logba

.[14] [15]

log48=

3
2
1.5000 Also called "Minkowski sausage".
log
2\left(1+\sqrt[3]{73-6\sqrt{87
}+\sqrt[3]}\right)
1.5236 cf. Chang & Zhang.[16]
log
2\left(1+\sqrt[3]{73-6\sqrt{87
}+\sqrt[3]}\right)
1.5236 Boundary of the twindragon curveCan be built with two dragon curves. One of the six 2-rep-tiles in the plane (can be tiled by two copies of itself, of equal size).

log23

1.5850 3-branches tree Each branch carries 3 branches (here 90° and 60°). The fractal dimension of the entire tree is the fractal dimension of the terminal branches. NB: the 2-branches tree has a fractal dimension of only 1.

log23

1.5850 Also the limiting shape of Pascal's triangle modulo 2.

log23

1.5850 Same limit as the triangle (above) but built with a one-dimensional curve.

log23

1.5850 Boundary of the T-square fractal The dimension of the fractal itself (not the boundary) is

log24=2

log\sqrt[\varphi]{\varphi

}(\varphi) = \varphi
1.61803 Built from two similarities of ratios

r

and

r2

, with

r=1/\varphi1/\varphi

. Its dimension equals

\varphi

because

({r2})\varphi+r\varphi=1

.

\varphi=(1+\sqrt{5})/2

(golden ratio).

1+log32

1.6309 Pascal triangle modulo 3 For a triangle modulo k, if k is prime, the fractal dimension is

1+

log
k\left(k+1
2

\right)

(cf. Stephen Wolfram[17]).

1+log32

1.6309 Built in the manner of the Sierpinski carpet, on an hexagonal grid, with 6 similitudes of ratio 1/3. The Koch snowflake is present at all scales.
3log\varphi
log(1+\sqrt{2

)}

1.6379 Fractal based on the Fibonacci word (or Rabbit sequence) Sloane A005614. Illustration : Fractal curve after 23 steps (F23 = 28657 segments).[18]

\varphi=(1+\sqrt{5})/2

(golden ratio).
Solution of

(1/3)s+(1/2)s+(2/3)s=1

1.6402 Attractor of IFS with 3 similarities of ratios 1/3, 1/2 and 2/3 Generalization : Providing the open set condition holds, the attractor of an iterated function system consisting of

n

similarities of ratios

cn

, has Hausdorff dimension

s

, solution of the equation coinciding with the iteration function of the Euclidean contraction factor:
n
\sum\nolimits
k=1
s
c
k

=1

.

log832=

5
3
1.6667 32-segment quadric fractal (1/8 scaling rule) see also: Built by scaling the 32 segment generator (see inset) by 1/8 for each iteration, and replacing each segment of the previous structure with a scaled copy of the entire generator. The structure shown is made of 4 generator units and is iterated 3 times. The fractal dimension for the theoretical structure is log 32/log 8 = 1.6667. Images generated with Fractal Generator for ImageJ.

1+log53

1.6826 Pascal triangle modulo 5 For a triangle modulo k, if k is prime, the fractal dimension is

1+

log
k\left(k+1
2

\right)

(cf. Stephen Wolfram).
Measured (box-counting) 1.7 Ikeda map attractor For parameters a=1, b=0.9, k=0.4 and p=6 in the Ikeda map

zn+1=a+bzn\exp\left[i\left[k-p/\left(1+\lfloorzn\rfloor2\right)\right]\right]

. It derives from a model of the plane-wave interactivity field in an optical ring laser. Different parameters yield different values.[19]

1+log105

1.6990 50 segment quadric fractal (1/10 scaling rule) Built by scaling the 50 segment generator (see inset) by 1/10 for each iteration, and replacing each segment of the previous structure with a scaled copy of the entire generator. The structure shown is made of 4 generator units and is iterated 3 times. The fractal dimension for the theoretical structure is log 50/log 10 = 1.6990. Images generated with Fractal Generator for ImageJ[20] .

4log52

1.7227 Built with Conway's Pinwheel tile.

log37

1.7712 Built with the Sphinx hexiamond tiling, removing two of the nine sub-sphinxes.[21]

log37

1.7712 Built by exchanging iteratively each hexagon by a flake of 7 hexagons. Its boundary is the von Koch flake and contains an infinity of Koch snowflakes (black or white).

log37

1.7712 Fractal H-I de Rivera Starting from a unit square dividing its dimensions into three equal parts to form nine self-similar squares with the first square, two middle squares (the one that is above and the one below the central square) are removed in each of the seven squares not eliminated the process is repeated, so it continues indefinitely.
log4
log(2+2\cos(85\circ))
1.7848 Generalizing the von Koch curve with an angle a chosen between 0 and 90°. The fractal dimension is then
log4
log(2+2\cosa)

\in[1,2]

.
0.63
log
2\left(3

+20.63\right)

1.8272 A self-affine fractal set Build iteratively from a p-by-q array on a square, with

p\leq

. Its Hausdorff dimension equals

logp\left(\sum\nolimits

p
k=1
a\right)
n
k
with

a=logqp

and

nk

is the number of elements in the

k

th column. The box-counting dimension yields a different formula, therefore, a different value. Unlike self-similar sets, the Hausdorff dimension of self-affine sets depends on the position of the iterated elements and there is no formula, so far, for the general case.
log6
log(1+\varphi)
1.8617 Built by exchanging iteratively each pentagon by a flake of 6 pentagons.

\varphi=(1+\sqrt{5})/2

(golden ratio).
solution of

6(1/3)s+5{(1/3\sqrt{3})}s=1

1.8687 Monkeys tree This curve appeared in Benoit Mandelbrot's "Fractal geometry of Nature" (1983). It is based on 6 similarities of ratio

1/3

and 5 similarities of ratio

1/3\sqrt{3}

.[22]

log38

1.8928 Each face of the Menger sponge is a Sierpinski carpet, as is the bottom surface of the 3D quadratic Koch surface (type 1).

log38

1.8928 Cantor set in 3 dimensions.

log34+log32=

log4+
log3
log2
log3

=

log8
log3
Generalization : Let F×G be the cartesian product of two fractals sets F and G. Then

\dimH(F x G)=\dimHF+\dimHG

. See also the 2D Cantor dust and the Cantor cube.

2log2x

where

x9-3x8+3x7-3x6+2x5+4x4-8x3+

8x2-16x+8=0

1.9340 Estimated by Duvall and Keesling (1999). The curve itself has a fractal dimension of 2.
2 See Ramachandrarao, Sinha & Sanyal.[23]

2

2 The boundary and the set itself have the same Hausdorff dimension.[24]

2

2 For determined values of c (including c belonging to the boundary of the Mandelbrot set), the Julia set has a dimension of 2.

2

2 Every space-filling curve filling the plane has a Hausdorff dimension of 2.

2

2

2

2 And a family of curves built in a similar way, such as the Wunderlich curves.

2

2 Can be extended in 3 dimensions.
2 Unlike the previous ones this space-filling curve is differentiable almost everywhere. Another type can be defined in 2D. Like the Hilbert Curve it can be extended in 3D.[25]

log\sqrt{2

} 2 = 2
2 And its boundary has a fractal dimension of 1.5236270862.[26]
2 L-system: F → F + F  -  F, angle = 120°.

log24=2

2 Its boundary is the Gosper island.
Solution of

7({1/3})s+6({1/3\sqrt{3}})s=1

2 Proposed by Mandelbrot in 1982,[27] it fills the Koch snowflake. It is based on 7 similarities of ratio 1/3 and 6 similarities of ratio

1/3\sqrt{3}

.

log24=2

2 Each tetrahedron is replaced by 4 tetrahedra.

log24=2

2 Also the Mandelbrot tree which has a similar pattern.
log2
log(2/\sqrt{2

)}=2

Every square generates two squares with a reduction ratio of

1/\sqrt{2}

.

log24=2

2 Each segment is replaced by a cross formed by 4 segments.
Measured 2.01 ± 0.01The fractal dimension of the Rössler attractor is slightly above 2. For a=0.1, b=0.1 and c=14 it has been estimated between 2.01 and 2.02.[28]
Measured 2.06 ± 0.01For parameters

\rho=40

,

\sigma=16

and

\beta=4

. See McGuinness (1983)[29]

4+cD+dD=(c+d)D

2<D<2.3 Pyramid surface Each triangle is replaced by 6 triangles, of which 4 identical triangles form a diamond based pyramid and the remaining two remain flat with lengths

c

and

d

relative to the pyramid triangles. The dimension is a parameter, self-intersection occurs for values greater than 2.3.[30]

log25

2.3219 Fractal pyramid Each square pyramid is replaced by 5 half-size square pyramids. (Different from the Sierpinski tetrahedron, which replaces each triangular pyramid with 4 half-size triangular pyramids).
log20
log(2+\varphi)
2.3296 Dodecahedron fractalEach dodecahedron is replaced by 20 dodecahedra.

\varphi=(1+\sqrt{5})/2

(golden ratio).

log313

2.3347 Extension in 3D of the quadratic Koch curve (type 1). The illustration shows the first (blue block), second (plus green blocks), third (plus yellow blocks) and fourth (plus clear blocks) iterations.
2.4739 The interstice left by the Apollonian spheres. Apollonian gasket in 3D. Dimension calculated by M. Borkovec, W. De Paris, and R. Peikert.[31]

log432=

5
2
2.50 Extension in 3D of the quadratic Koch curve (type 2). The illustration shows the second iteration.
log\left(\sqrt{7
-
6
1
3

\right)}{log(\sqrt2-1)}

2.529 The iteration n is built with 8 cubes of iteration n−1 (at the corners) and 12 cubes of iteration n-2 (linking the corners). The contraction ratio is

\sqrt{2}-1

.
log12
log(1+\varphi)
2.5819 Each icosahedron is replaced by 12 icosahedra.

\varphi=(1+\sqrt{5})/2

(golden ratio).

1+log23

2.5849 Each segment is replaced by a cross formed by 6 segments.

1+log23

2.5849 Each octahedron is replaced by 6 octahedra.

1+log23

2.5849 Each equilateral triangular face is cut into 4 equal triangles.Using the central triangle as the base, form a tetrahedron. Replace the triangular base with the tetrahedral "tent".
log3
log(3/2)
2.7095 Start with a 6-sided polyhedron whose faces are isosceles triangles with sides of ratio 2:2:3 . Replace each polyhedron with 3 copies of itself, 2/3 smaller.[32]

log320

2.7268 And its surface has a fractal dimension of

log320

, which is the same as that by volume.

log28=3

3 A Hilbert curve extended to 3 dimensions.

log28=3

3 A Lebesgue curve extended to 3 dimensions.

log28=3

3 A Moore curve extended to 3 dimensions.

log28=3

3 A H-fractal extended to 3 dimensions.[33]

3

(conjectured)
(to be confirmed) Extension of the Mandelbrot set (power 9) in 3 dimensions[34]

Random and natural fractals

Hausdorff dimension
(exact value)
Hausdorff dimension
(approx.)
Name Illustration Remarks
1
2
0.5 The zeros of a Wiener process (Brownian motion) are a nowhere dense set of Lebesgue measure 0 with a fractal structure.[35]
Solution of
s
E(C
1

+

s)=1
C
2
where

E(C1)=0.5

and

E(C2)=0.3

0.7499 a random Cantor set with 50% - 30% Generalization: at each iteration, the length of the left interval is defined with a random variable

C1

, a variable percentage of the length of the original interval. Same for the right interval, with a random variable

C2

. Its Hausdorff Dimension

s

satisfies:
s
E(C
1

+

s)=1
C
2
(where

E(X)

is the expected value of

X

).
Solution of

s+1=12 ⋅ 2-(s+1)-6 ⋅ 3-(s+1)

1.144...von Koch curve with random intervalThe length of the middle interval is a random variable with uniform distribution on the interval (0,1/3).
Measured1.22 ± 0.02Coastline of IrelandValues for the fractal dimension of the entire coast of Ireland were determined by McCartney, Abernethy and Gault[36] at the University of Ulster and Theoretical Physics students at Trinity College, Dublin, under the supervision of S. Hutzler.[37]

Note that there are marked differences between Ireland's ragged west coast (fractal dimension of about 1.26) and the much smoother east coast (fractal dimension 1.10)

Measured1.25Coastline of Great BritainFractal dimension of the west coast of Great Britain, as measured by Lewis Fry Richardson and cited by Benoît Mandelbrot.[38]
log4
log3
1.2619 von Koch curve with random orientation One introduces here an element of randomness which does not affect the dimension, by choosing, at each iteration, to place the equilateral triangle above or below the curve.
4
3
1.333 Boundary of Brownian motion (cf. Mandelbrot, Lawler, Schramm, Werner).[39]
4
3
1.333 Polymer in 2D Similar to the Brownian motion in 2D with non-self-intersection.[40]
4
3
1.333 Percolation front in 2D, Corrosion front in 2D Fractal dimension of the percolation-by-invasion front (accessible perimeter), at the percolation threshold (59.3%). It's also the fractal dimension of a stopped corrosion front.
1.40 When limited by diffusion, clusters combine progressively to a unique cluster of dimension 1.4.
2-1
2
1.5Graph of a regular Brownian function (Wiener process) Graph of a function

f

such that, for any two positive reals

x

and

x+h

, the difference of their images

f(x+h)-f(x)

has the centered gaussian distribution with variance

h

. Generalization: the fractional Brownian motion of index

\alpha

follows the same definition but with a variance

h2\alpha

, in that case its Hausdorff dimension equals

2-\alpha

.
Measured1.52See J. Feder.[41]
Measured1.55 Random walk in a square lattice that avoids visiting the same place twice, with a "go-back" routine for avoiding dead ends.
5
3
1.66Polymer in 3D Similar to the Brownian motion in a cubic lattice, but without self-intersection.
1.70 In 2 dimensions, clusters formed by diffusion-limited aggregation, have a fractal dimension of around 1.70.
log(9 ⋅ 0.75)
log3
1.7381Fractal percolation with 75% probabilityThe fractal percolation model is constructed by the progressive replacement of each square by a 3-by-3 grid in which is placed a random collection of sub-squares, each sub-square being retained with probability p. The "almost sure" Hausdorff dimension equals
log(9p)
log3
.
7
4
1.75 2D percolation cluster hull The hull or boundary of a percolation cluster. Can also be generated by a hull-generating walk,[42] or by Schramm-Loewner Evolution.
91
48
1.8958 In a square lattice, under the site percolation threshold (59.3%) the percolation-by-invasion cluster has a fractal dimension of 91/48.[43] Beyond that threshold, the cluster is infinite and 91/48 becomes the fractal dimension of the "clearings".
log2
log\sqrt{2
} = 2
2 Or random walk. The Hausdorff dimensions equals 2 in 2D, in 3D and in all greater dimensions (K.Falconer "The geometry of fractal sets").
Measured Around 2 Distribution of galaxy clusters From the 2005 results of the Sloan Digital Sky Survey.[44]
2.5 Balls of crumpled paper When crumpling sheets of different sizes but made of the same type of paper and with the same aspect ratio (for example, different sizes in the ISO 216 A series), then the diameter of the balls so obtained elevated to a non-integer exponent between 2 and 3 will be approximately proportional to the area of the sheets from which the balls have been made.[45] Creases will form at all size scales (see Universality (dynamical systems)).
2.50 In 3 dimensions, clusters formed by diffusion-limited aggregation, have a fractal dimension of around 2.50.
2.50 Their appearance and growth appear to be related to the process of diffusion-limited aggregation or DLA.
3-1
2
2.5regular Brownian surfaceA function

f:R2\toR

, gives the height of a point

(x,y)

such that, for two given positive increments

h

and

k

, then

f(x+h,y+k)-f(x,y)

has a centered Gaussian distribution with variance

\sqrt{h2+k2}

. Generalization: the fractional Brownian surface of index

\alpha

follows the same definition but with a variance

(h2+k2)\alpha

, in that case its Hausdorff dimension equals

3-\alpha

.
Measured 2.52 3D percolation cluster In a cubic lattice, at the site percolation threshold (31.1%), the 3D percolation-by-invasion cluster has a fractal dimension of around 2.52. Beyond that threshold, the cluster is infinite.
Measured and calculated~2.7San-Hoon Kim used a direct scanning method and a cross section analysis of a broccoli to conclude that the fractal dimension of it is ~2.7.[46]
Measured ~2.8 Measured with segmented three-dimensional high-resolution magnetic resonance images[47]
Measured and calculated~2.8San-Hoon Kim used a direct scanning method and a mathematical analysis of the cross section of a cauliflower to conclude that the fractal dimension of it is ~2.8.
2.97 Lung surface The alveoli of a lung form a fractal surface close to 3.
Calculated

\in(0,2)

This is an example of a multifractal distribution. However, by choosing its parameters in a particular way we can force the distribution to become a monofractal.[48]

See also

Further reading

External links

Notes and References

  1. Erik . Aurell . On the metric properties of the Feigenbaum attractor . Journal of Statistical Physics . 47 . 3–4 . 439–458 . May 1987 . 10.1007/BF01007519 . 1987JSP....47..439A . 122213380 .
  2. A. Yu . Cherny . E.M. . Anitas . A.I. . Kuklin . M. . Balasoiu . V.A. . Osipov . The scattering from generalized Cantor fractals . J. Appl. Crystallogr. . 43 . 4. 790–7 . 2010 . 10.1107/S0021889810014184 . 0911.2497 . 94779870 .
  3. Tsang, K. Y. . Dimensionality of Strange Attractors Determined Analytically . Phys. Rev. Lett. . 57. 12. 1390–1393 . 1986. 10033437 . 10.1103/PhysRevLett.57.1390. 1986PhRvL..57.1390T.
  4. Book: Falconer, Kenneth . Kenneth Falconer (mathematician) . Fractal Geometry: Mathematical Foundations and Applications . John Wiley & Sons, Ltd. . 1990–2003 . 978-0-470-84862-3 . true . xxv.
  5. Damanik . D. . Embree . M. . Gorodetski . A. . S. . Tcheremchantse . The Fractal Dimension of the Spectrum of the Fibonacci Hamiltonian . Commun. Math. Phys. . 280 . 2 . 499–516 . 2008 . 10.1007/s00220-008-0451-3 . 0705.0338. 2008CMaPh.280..499D . 12245755 .
  6. Book: Vaz, Cristina . Noções Elementares Sobre Dimensão . 9788565054867 . 2019.
  7. Book: Mandelbrot, Benoit . Gaussian self-affinity and Fractals . 978-0-387-98993-8 . 2002 . Springer .
  8. Messaoudi, Ali. Frontième de numération complexe", matwbn.icm.edu.pl. Accessed: 27 October 2018.
  9. Ngai, Sirvent, Veerman, and Wang (October 2000). "On 2-Reptiles in the Plane 1999", Geometriae Dedicata, Volume 82. Accessed: 29 October 2018.
  10. Duda, Jarek (March 2011). "The Boundary of Periodic Iterated Function Systems", Wolfram.com.
  11. McMullen, Curtis T. (3 October 1997). "Hausdorff dimension and conformal dynamics III: Computation of dimension", Abel.Math.Harvard.edu. Accessed: 27 October 2018.
  12. Chang, Angel and Zhang, Tianrong. Web site: On the Fractal Structure of the Boundary of Dragon Curve . 9 February 2019 . https://web.archive.org/web/20110614063904/http://classes.yale.edu/Fractals/CircInvFrac/CircDim/CircDim2.html . 14 June 2011 . bot: unknown . pdf
  13. Mandelbrot, B. B. (1983). The Fractal Geometry of Nature, p.48. New York: W. H. Freeman. . Cited in:
  14. Shen. Weixiao. 2018. Hausdorff dimension of the graphs of the classical Weierstrass functions. Mathematische Zeitschrift. en. 289. 1–2. 223–266. 10.1007/s00209-017-1949-1. 0025-5874. 1505.03986. 118844077.
  15. N. Zhang. The Hausdorff dimension of the graphs of fractal functions. (In Chinese). Master Thesis. Zhejiang University, 2018.
  16. http://poignance.coiraweb.com/math/Fractals/Dragon/Bound.html Fractal dimension of the boundary of the dragon fractal
  17. Web site: Fractal dimension of the Pascal triangle modulo k . 2 October 2006 . 15 October 2012 . https://web.archive.org/web/20121015154035/http://www.stephenwolfram.com/publications/articles/ca/84-geometry/1/text.html . dead .
  18. http://hal.archives-ouvertes.fr/hal-00367972/en/ The Fibonacci word fractal
  19. James . Theiler . Estimating fractal dimension . J. Opt. Soc. Am. A . 7 . 6 . 1055–73 . 1990 . 10.1364/JOSAA.7.001055 . 1990JOSAA...7.1055T .
  20. http://rsb.info.nih.gov/ij/plugins/fractal-generator.html Fractal Generator for ImageJ
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