# Generate a smoothly varying set of colors

### Description

`colorpanel`

generate a set of colors that varies
smoothly. `redgreen`

, `greenred`

, `bluered`

, and
`redblue`

generate red-black-green, green-black-red,
red-white-blue, and blue-white-red colorbars, respectively.
colors

### Usage

1 2 3 4 5 | ```
colorpanel(n, low, mid, high)
redgreen(n)
greenred(n)
bluered(n)
redblue(n)
``` |

### Arguments

`n` |
Desired number of color elements in the panel. |

`low, mid, high` |
Colors to use for the Lowest, middle,
and highest values. |

### Details

The values for `low, mid, high`

can be given as
color names ('red'), plot color index (2=red), and HTML-style RGB,
("\#FF0000"=red).

If `mid`

is supplied, then the returned color panel will consist
of `n - floor(n/2)`

HTML-style RGB elements which vary smoothly
between `low`

and `mid`

, then between `mid`

and
`high`

. Note that if `n`

is even, the color `mid`

will
occur twice at the center of the sequence.

If `mid`

is omitted, the color panel will vary
smoothly beween `low`

and `high`

.

### Value

Vector of HTML-style RGB colors.

### Author(s)

Gregory R. Warnes greg@warnes.net

### See Also

`colors `

### Examples

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | ```
showpanel <- function(col)
{
image(z=matrix(1:100, ncol=1), col=col, xaxt="n", yaxt="n" )
}
par(mfrow=c(3,3))
# two colors only:
showpanel(colorpanel(8,low="red",high="green"))
# three colors
showpanel(colorpanel(8,"red","black","green"))
# note the duplicatation of black at the center, using an odd
# number of elements resolves this:
showpanel(colorpanel(9,"red","black","green"))
showpanel(greenred(64))
showpanel(redgreen(64))
showpanel(bluered(64))
showpanel(redblue(64))
``` |