scale_gradient

scale_colour_gradient(name=NULL, low="#3B4FB8", high="#B71B1A", space="rgb", breaks=NULL, labels=NULL, limits=NULL, trans="identity", ...)
scale_fill_gradient(name=NULL, low="#3B4FB8", high="#B71B1A", 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
• high: colour at high end of scale
• 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_gradient2: continuous colour scale with midpoint
• colorRamp: for details of interpolation algorithm

Examples

> # It's hard to see, but look for the bright yellow dot 
> # in the bottom right hand corner 
> dsub <- subset(diamonds, x > 5 & x < 6 & y > 5 & y < 6) 
> (d <- qplot(x, y, data=dsub, colour=z)) 
  
> # That one point throws our entire scale off.  We could 
> # remove it, or manually tweak the limits of the scale 
>  
> # Tweak scale limits.  Any points outside these 
> # limits will not be plotted, but will continue to affect the 
> # calculate of statistics, etc 
> d + scale_colour_gradient(limits=c(3, 10)) 
  
> d + scale_colour_gradient(limits=c(3, 4)) 
  
> # Setting the limits manually is also useful when producing 
> # multiple plots that need to be comparable 
>  
> # Alternatively we could try transforming the scale: 
> d + scale_colour_gradient(trans = "log") 
  
> d + scale_colour_gradient(trans = "sqrt") 
  
>  
> # Other more trivial manipulations, including changing the name 
> # of the scale and the colours. 
>  
> d + scale_colour_gradient("Depth") 
  
> d + scale_colour_gradient(expression(Depth[mm])) 
  
>  
> d + scale_colour_gradient(limits=c(3, 4), low="red") 
  
> d + scale_colour_gradient(limits=c(3, 4), low="red", high="white") 
  
> # Much slower 
> d + scale_colour_gradient(limits=c(3, 4), low="red", high="white", space="Lab") 
  
> d + scale_colour_gradient(limits=c(3, 4), space="Lab") 
  
>  
> # scale_fill_continuous works similarly, but for fill colours 
> (h <- qplot(x - y, data=dsub, geom="histogram", binwidth=0.01, fill=..count..)) 
  
> h + scale_fill_continuous(low="black", high="pink", limits=c(0,3100)) 
  

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© Hadley Wickham 2010