R: Create color table

colorize {ursa}

R Documentation

Create color table

Description

colorize assigns color table to raster image.

Usage

colorize(obj, value = NULL, breakvalue = NULL, name = NULL, pal = NULL, inv = NA,
         stretch = c("default", "linear", "equal", "mean", "positive",
                     "negative", "diff", "category", "julian", "date", "time",
                     "slope", "conc", "sd", "significance", "bathy",
                     "grayscale", "greyscale", ".onetoone"),
         minvalue = NA, maxvalue = NA, byvalue = NA, ltail = NA, rtail = NA, tail = NA,
         ncolor = NA, nbreak = NA, interval = 0L, ramp = TRUE, byte = FALSE,
         lazyload = FALSE, reset = FALSE, origin = "1970-01-01" ,format = "",
         alpha = "", colortable = NULL, verbose = FALSE, ...)
                          
palettize(...) ## wrapper for non-spatial vectors

Arguments

`obj`	`ursaRaster` object or one-dimension numeric or character vector.
`value`	Numeric. Values to be assigned to categories.
`breakvalue`	Numeric. Values to be assigned to intervals.
`name`	Character. Names of categories.
`pal`	Function or character. If function then value should corresponded to function, which creates a vector of colors. If character then values should correponded to R color names or hexadecimal string of the form "#RRGGBB" or "#RRGGBBAA".
`inv`	Logical. Invert sequence of colors.
`stretch`	Character. Either kind of value transformation (`"linear", "equal"`) or pre-defined options with palette specification (`"positive", "data", "significance"`, etc)
`minvalue`	Numeric. Lower range limit.
`maxvalue`	Numeric. Upper range limit.
`byvalue`	Numeric. Increment of the sequence from `minvalue` to `maxvalue`.
`ltail`	Numeric. Partition of omitted values at left tail.
`rtail`	Numeric. Partition of omitted values at right tail.
`tail`	Numeric. Partition of omitted values at both tail. If length of `tail` is 2 then left and right tails may differ.
`ncolor`	Numeric or interer. Number of desired colors (or categories)
`nbreak`	Numeric or interer. Number of desired separators between colors.
`interval`	Integer. How to underwrite categories? Use direct
`ramp`	Logical. Is color ramp required?
`byte`	Logical. Forcing to produce color table for storage in byte format (not more than 255 colors). Default is `FALSE`.
`lazyload`	Logical. If `FALSE` then raster is reclassified to categories. If `TRUE` then color table is created without any change to source raster. Default is `FALSE`.
`reset`	Logical. If `TRUE` and source raster has color table, then this color table is destroyed, and new one is created. Default is `FALSE`.
`origin`	Character. Origin for `stretch="date"` (passed to function `as.Date`) and `stretch="time"` (passed to function `as.POSIXct`). See desription of `orogin` in respective functions. Default is "1970-01-01".
`format`	Character. Format date/time objects for arguments `stretch` with values "date", "time", or "julian". Default is "" (character of length 0).
`alpha`	Character or numeric. The characteristics of transparency. If character, then hexadecimal values between "00" and "FF" are allowed, and then coerced to numeric value between 0 and 255. If numeric, and `⁠0 <= alpha <= 1⁠`, then `alpha` is multiplied to 255. `alpha=0` means full transparency, `alpha=255` means full opacity. Default is ""; if palette has no alpha channel, then `alpha` is assign to `"FF"`.
`colortable`	Object of class `ursaColorTable` or object of class `ursaRaster` with color table. Reference color table. Is specified, then all other arguments are ignored, expexted `lazyload`. Default is `NULL` (unspecified).
`verbose`	Logical. Some output in console. Primarily for debug purposes.
`...`	For `colorize()`: If `pal` is a function, and argument names are in the format "`pal.*`" then prefix "`pal.`" is omitted, and the rest part is used for argument names, which are passed to `pal` function. For `palettize()`: Arguments, which are passed to `colorize()`.

Details

palettize is a wrapper ursa_colortable(colorize(...)) to return color table for one-dimensional numeric or character vector.

colortable is designed to prepare pretty thematic maps.

Color rampimg (ramp=TRUE) is not quick in computatons and has no effective labelling. It is intoduced to visualize non-thematic maps, and it is assumed that labeling can be omitted for such maps.

The labelling implementation is based on some improvements of pretty function. The notation of intervals is mixed by brackets and comparative symbols, for example: "<=1.5","(1.5,2.5]","(2.5,3.5]",">3.5"

Reserved values for interval:

0L or FALSE - no interlavs. Values are interpreted as category, even if they are in non-nominal scale
1L or TRUE - each category corresponds to interval. The low limit of lowest category is -Inf. The high limit of highest category is +Inf
2L - different implementation of interval=1. In some cases may relult more pretty labeling.

If breaks is numerical vector and colors has zero length, then it is assumed interal scaling, and interval=1L is assigned to unspecified interval

Finite values of extreme intervals are neccessary sometimes, however this option is not implemented currently

Keywords for stretch to create pre-defined color tables:

"positive" - lower limit is 0. Palette is "Oranges"
"negative" - higher limit is 0. Palette is "Purples"
"grayscale", "greyscale" - palette is "Greys". Usually used for raw satellite images.
"mean" - designed for common thematic maps and for averaged map across set of maps. Palette is "Spectral"
"sd" - designed for spatial mapping of standard deviation across set of maps. Palette is "YlGnBu"
"diff" - diverge palette "RdBu". Absolute values of lower and upper limits are equal, zero is in the middle of palette. Designed for anomaly maps.
"slope" - is similar to diff but without extreme colors, which are reserved for contouring of statistically significant areas.
"significance" - desiged to illustrate statistically significant areas of slope. The realisation is colortable(obj, value=c(-0.999, -0.99, -0.95, -0.9, -0.5, +0.5, +0.9, +0.95, +0.99, +0.999), interval=1L, palname="RdBu")
"category" - Values are interpreted in nominal scale. Palette is based on random colors from "Pairs" palette.
"conc" - designed for visualization of sea ice concentration data, which have lower limit 0 and higher limit 100. Palette is "Blues"
"bathy" - designed for ocean depth (bathymetry) maps. Internally colorize(obj, stretch="equal",interval=1L, palname="Blues", inv=TRUE) is used to detect the crossing from shelf waters to deep water basin. Better practice is to do second step with manual specification of value argument.
"internal" - continuous colors, designed for conversion to greyscale with keeping of intensities.
"default" - allowing to detect stretch by intuition, without any strong mathematical criteria

It is allowed manual correction of labels using followed code example: names(ursa_colortable(x)) <- c("a<=0","0<a<=1","a>1")

Value

Object of class ursaRaster with named character vector of item $colortable

Author(s)

Nikita Platonov platonov@sevin.ru

Examples

session_grid(NULL)
a <- pixelsize()-350
print(a)
b1 <- colorize(a,ramp=FALSE)
print(ursa_colortable(b1))
b2 <- colorize(a,interval=1,stretch="positive",ramp=FALSE)
print(ursa_colortable(b2))
b3 <- colorize(a,interval=2,stretch="positive",ramp=FALSE)
print(ursa_colortable(b3))
b4 <- colorize(a,value=c(150,250),interval=1)
print(ursa_colortable(b4))
names(ursa_colortable(b4)) <- c("x<=150","150<x<=250","x>250")
print(ursa_colortable(b4))
display(b4)

[Package ursa version 3.10.4 Index]