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If I have data like this
DF <- data.frame(
date = seq(Sys.Date()-1000, len=1000, by="1 day")[sample(1000, 500)],
price = runif(500)
)
How do I plot e.g. mean of price in the function of time, e.g. in months, using ggplot2?
642
ggplot2 is a plotting package that provides helpful commands to create complex plots from data in a data frame. It provides a more programmatic interface for specifying what variables to plot, how they are displayed, and general visual properties.
Geoms. A layer combines data, aesthetic mapping, a geom (geometric object), a stat (statistical transformation), and a position adjustment. Typically, you will create layers using a geom_ function, overriding the default position and stat if needed.
ggplot() initializes a ggplot object. It can be used to declare the input data frame for a graphic and to specify the set of plot aesthetics intended to be common throughout all subsequent layers unless specifically overridden.
You need to convert your dates into months using cut(,"months"), then apply mean to each month using ggplot stat_summary. Here's how to do it in qplot, which is a compact convenience wrapper to ggplot.
qplot(as.Date(cut(date,"months")),
price, data=DF, stat="summary", fun.y="mean", xlab="date")
alt text http://www.imagechicken.com/uploads/1264786975079660800.png
Base plot can also do it:
plot(aggregate(DF$price, list(as.Date(cut(DF$date, "month"))), mean))
alt text http://www.imagechicken.com/uploads/1264786673030283100.png
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