# legend.scale: Color scale legend In autoimage: Multiple Heat Maps for Projected Coordinates

## Description

`legend.scale` plots a color gradient with an associated quantitative scale.

## Usage

 ```1 2``` ```legend.scale(zlim, col = viridisLite::viridis(12), horizontal = TRUE, breaks, axis.args) ```

## Arguments

 `zlim` A two-dimensional vector containing the minimum and maximum quantitative limits, respectively, for the color scale. `col` A vector of colors used for the color scale. Typically, this is a gradient of colors. The default is the 12 colors generated by `viridisLite::viridis(12)`. `horizontal` A logical value indicating whether the legend should extend horizontally (`TRUE`) or vertically (`FALSE`). The default is `TRUE`. `breaks` The sequence of values defining the partition of `zlim`. The length should be one more than then number of colors. If not specified, then equidistant breaks are used. `axis.args` A list of named elements corresponding to the arguments of the `axis` function. This is used to modify the appearance of the scale of the legend. See Examples.

## Details

The length of the `col` vector indicates the number of partitions for the quantitative range.

## References

The code for this function is derived from the internals of the `image.plot` function written by Doug Nychka and from the `image.scale` function written by Marc Taylor and discussed at http://menugget.blogspot.com/2013/12/new-version-of-imagescale-function.html.

`image`, `image.plot`, `axis`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30``` ```# default horizontal scale legend.scale(c(0, 1)) # default vertical scale legend.scale(c(0, 1), horizontal = FALSE) # different color scheme with 24 colors legend.scale(c(0, 1), col = cm.colors(24)) # irregular color breaks legend.scale(c(0, 1), col = heat.colors(4), breaks = c(0, 0.5, 0.75, 0.875, 1)) # irregular color breaks with modified ticks and vertical # orientation of labels legend.scale(c(0, 1), col = heat.colors(4), breaks = c(0, 0.5, 0.75, 0.875, 1), axis.args = list(at = c(0, 0.5, 0.75, 0.875, 1), las = 2)) # change size of axis labels legend.scale(c(0, 1), axis.args = list(cex.axis = 2)) # change color of axis labels and ticks blue.axes <- list(col.axis = "blue", col.ticks = "blue") legend.scale(c(0, 1), axis.args = blue.axes) # log base 10 values with colors labeled on original scale options(scipen = 2) log.axis <- list(at = 0:6, labels = 10^(0:6), las = 2) legend.scale(c(0, 6), col = heat.colors(6), axis.args = log.axis) ```