scale_date

scale_x_date(name=NULL, limits=NULL, major=NULL, minor=NULL, format=NULL, ...)
scale_y_date(name=NULL, limits=NULL, major=NULL, minor=NULL, format=NULL, ...)

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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
• limits: numeric vector of length 2, giving the extent of the scale
• major: NULL
• minor: NULL
• format: NULL

Returns

This function returns a scale object.

See also

• scale_discrete: Discrete position scales

Examples

> # We'll start by creating some nonsense data with dates 
> df <- data.frame( 
+   date = seq(Sys.Date(), len=100, by="1 day")[sample(100, 50)], 
+   price = runif(50) 
+ ) 
> df <- df[order(df$date), ] 
> dt <- qplot(date, price, data=df, geom="line") + opts(aspect.ratio = 1/4) 
>  
> # We can control the format of the labels, and the frequency of 
> # the major and minor tickmarks.  See ?format.Date and ?seq.Date 
> # for more details. 
> dt + scale_x_date() 
  
> dt + scale_x_date(format="%m/%d") 
  
> dt + scale_x_date(format="%W") 
  
> dt + scale_x_date(major="months", minor="weeks", format="%b") 
  
> dt + scale_x_date(major="months", minor="3 days", format="%b") 
  
> dt + scale_x_date(major="years", format="%b-%Y") 
  
>  
> # The date scale will attempt to pick sensible defaults for 
> # major and minor tick marks 
> qplot(date, price, data=df[1:10,], geom="line") 
  
> qplot(date, price, data=df[1:4,], geom="line") 
  
>  
> df <- data.frame( 
+   date = seq(Sys.Date(), len=1000, by="1 day"), 
+   price = runif(500) 
+ ) 
> qplot(date, price, data=df, geom="line") 
  
>  
> # A real example using economic time series data 
> qplot(date, psavert, data=economics) 
  
> qplot(date, psavert, data=economics, geom="path") 
  
>  
> end <- max(economics$date) 
> last_plot() + scale_x_date(lim = c(as.Date("2000-1-1"), end)) 
  
> last_plot() + scale_x_date(lim = c(as.Date("2005-1-1"), end)) 
  
> last_plot() + scale_x_date(lim = c(as.Date("2006-1-1"), end)) 
  
>  
> # If we want to display multiple series, one for each variable 
> # it's easiest to first change the data from a "wide" to a "long" 
> # format: 
> em <- melt(economics, id = "date") 
>  
> # Then we can group and facet by the new "variable" variable 
> qplot(date, value, data = em, geom = "line", group = variable) 
  
> qplot(date, value, data = em, geom = "line", group = variable) + 
+   facet_grid(variable ~ ., scale = "free_y") 
  

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© Hadley Wickham 2010