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Strange "Peacock like" Images drawn by R
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Basic Program

x <- seq(-3, 3, length=1000)
y <- x
f <- function(x, y){ x^2 + y^2 }
z <- outer(x, y, f)
image(z)

click to enlarge (new window)
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Here, if you replace last line by "iamge(z, col=z)", you'll get a strange image!

x <- seq(-3, 3, length=1000)
y <- x
f <- function(x, y){ x^2 + y^2 }
z <- outer(x, y, f)
image(z, col=z)

click to enlarge (new window)
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Next figures show images when last line was replaced by "image(z, col=t*z)"
and t is increased from 0.1 to 0.9 by 0.1.
image(z, 0.1*z)

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image(z, 0.2*z)

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image(z, 0.3*z)

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image(z, 0.4*z)

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image(z, 0.5*z)

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image(z, 0.6*z)

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image(z, 0.7*z)

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image(z, 0.8*z)

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image(z, 0.9*z)

click to enlarge
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When "f" is replaced by "x*y", another image appears.

x <- seq(-3, 3, length=1000)
y <- x
f <- function(x, y){ x*y }
z <- outer(x, y, f)
image(z, col=abs(z))

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image(z, 0.5*abs(z))

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image(z, 3*abs(z))

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image(z, 10*abs(z))

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Next let's replace "f" by "x^2 - y^2".

x <- seq(-3, 3, length=1000)
y <- x
f <- function(x, y){ x^2 - y^2 }
z <- outer(x, y, f)
image(z, col=abs(z))

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image(z, 0.2*abs(z))

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image(z, 0.3*abs(z))

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image(z, 0.4*abs(z))

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The case in which "f" is "x^2+(y-abs(x)^(2/3))^2".

x <- seq(-3, 3, length=1000)
y <- x
f <- function(x, y){ x^2+(y-abs(x)^(2/3))^2 }
z <- outer(x, y, f)
image(z, col=0.5*z)

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image(z, 0.1*z)

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image(z, 0.2*z)

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image(z, 0.3*z)

click to enlarge
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