scale_gradient2

scale_colour_gradient2(name=NULL, low=muted("red"), mid="white", high=muted("blue"), midpoint=0, space="rgb", breaks=NULL, labels=NULL, limits=NULL, trans="identity", ...)
scale_fill_gradient2(name=NULL, low=muted("red"), mid="white", high=muted("blue"), midpoint=0, space="rgb", breaks=NULL, labels=NULL, limits=NULL, trans="identity", ...)

What do you think of the documentation? Please let me know by filling out this short online survey.

Parameters

Parameters control the appearance of the scale. In addition to the parameters listed below (if any), any aesthetic can be used as a parameter, in which case it will override any aesthetic mapping.

• name: name of scale to appear in legend or on axis. Maybe be an expression: see ?plotmath
• low: colour at low end of scale
• mid: colour at mid point of scale
• high: colour at high end of scale
• midpoint: position of mid point of scale, defaults to 0
• space: colour space to interpolate through, rgb or Lab, see ?colorRamp for details
• breaks: numeric vector indicating where breaks should lie
• labels: character vector giving labels associated with breaks
• limits: numeric vector of length 2, giving the extent of the scale
• trans: a transformer to use
• ...: other arguments

Returns

This function returns a scale object.

See also

• scale_gradient: continuous colour scale
• colorRamp: for details of interpolation algorithm

Examples

> dsub <- subset(diamonds, x > 5 & x < 6 & y > 5 & y < 6) 
> dsub$diff <- with(dsub, sqrt(abs(x-y))* sign(x-y)) 
> (d <- qplot(x, y, data=dsub, colour=diff)) 
  
>  
> d + scale_colour_gradient2() 
  
> # Change scale name 
> d + scale_colour_gradient2(expression(sqrt(abs(x - y)))) 
  
> d + scale_colour_gradient2("Difference\nbetween\nwidth and\nheight") 
  
>  
> # Change limits and colours 
> d + scale_colour_gradient2(limits=c(-0.2, 0.2)) 
  
>  
> # Using "muted" colours makes for pleasant graphics 
> # (and they have better perceptual properties too) 
> d + scale_colour_gradient2(low="red", high="blue") 
  
> d + scale_colour_gradient2(low=muted("red"), high=muted("blue")) 
  
>  
> # Using the Lab colour space also improves perceptual properties 
> # at the price of slightly slower operation 
> d + scale_colour_gradient2(space="Lab") 
  
>  
> # About 5% of males are red-green colour blind, so it's a good 
> # idea to avoid that combination 
> d + scale_colour_gradient2(high=muted("green")) 
  
>  
> # We can also make the middle stand out 
> d + scale_colour_gradient2(mid=muted("green"), high="white", low="white") 
  
>  
> # or use a non zero mid point 
> (d <- qplot(carat, price, data=diamonds, colour=price/carat)) 
  
> d + scale_colour_gradient2(midpoint=mean(diamonds$price / diamonds$carat)) 
  
>  
> # Fill gradients work much the same way 
> p <- qplot(letters[1:5], 1:5, fill= c(-3, 3, 5, 2, -2), geom="bar") 
> p + scale_fill_gradient2("fill") 
  
> # Note how positive and negative values of the same magnitude 
> # have similar intensity 

What do you think of the documentation? Please let me know by filling out this short online survey.

© Hadley Wickham 2010