tim.colors {fields} | R Documentation

## Some useful color tables for images.

### Description

Two color scales useful for image plots: a pleasing rainbow style color table patterned after that used in Matlab by Tim Hoar and also a simple colr interpolation between two colors passing through white.

### Usage

    tim.colors(n = 64)
    two.colors(n=256, start="darkgreen", end="red", middle="white")
    designer.colors( n=256, col= c("darkgreen", "white", "darkred"),
                                  x= seq(0,1,, length(col)) )

### Arguments

`n` | Number of color levels. The setting `n`=64 is the orignal definition.
`start` | Starting color for lowest values in color scale
`end` | Ending color.
`middle` | Color scale passes through this color at halfway
`col` | A list of colors (names or hex values) to interpolate
`x` | Positions of colors on a [0,1] scale. Default is to assume that the x values are equally spacesd from 0 to 1.

### Details

The color in R can be represented as three vectors in RGB coordinates and these coordinates are interpolated separately using a cubic spline to give color values that intermediate to the specified colors.

Ask Tim Hoar about tim.colors! He is a matlab black belt and this is his favorite scale in that system. `two.colors` is really about three different colors. For other colors try `fields.color.picker` to view possible choices. `start="darkgreen", end="azure4"` are the options used to get a nice color scale for rendering aerial photos of ski trails. (See http://www.image.ucar.edu/Data/MJProject.)

`designer.color` is the master function for two.colors and tim.colors. It can be useful if one wants to customize the color table to match quantiles of a distribution. e.g. if the median of the data is at .3 with respect to the range then set `x` equal to c(0,.3,1) and specify three colors to provide a transtion that matches the median value. In fields language this function interpolates between a set of colors at locations x. While you can be creative about these colors just using another color scale as the basis is easy. For example

`designer.color( 256, rainbow(4), x= c( 0,.2,.8,1.0))`

leaves the choice of the colors to Dr. R after a thunderstorm.

### Value

A vector giving the colors in a hexadecimal format.

### See Also

topo.colors, terrain.colors, image.plot, quilt.plot, grey.scale, fields.color.picker

### Examples

    tim.colors(10)
    # returns an array of 10 strings in hex format
    #e.g. (red, green,  blue) values of   (16,255, 239)
    # translates to "#10FFEF" .

    # veiw some color table choices
    set.panel( 1,3)
    par( pty="s")
    z<- outer( 1:20,1:20, "+")

    image( z, col=tim.colors( 200)) # 200 levels

    image( z, col=two.colors() )

    coltab<- designer.colors(col=c("blue", "grey", "green"),  x= c( 0,.3,1) )
    image( z, col= coltab )

    # peg colors at some desired quantiles  of data.
    # NOTE need 0 and 1 for the color scale to make sense
    x<- quantile( c(z), c(0,.25,.5,.75,1.0) )
    # scale these to [0,1]
    zr<- range( c(z))
    x<- (x-zr[1])/ (zr[2] - zr[1])

    coltab<- designer.colors(256,rainbow(5), x)
    image( z, col= coltab ) # see image.plot for adding all kinds of legends

    # colors now change at quantiles of data

    set.panel()

[Package fields version 6.01 Index]