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", ...)

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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 

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© Hadley Wickham 2012