[R] Lattice, combine histogram and line graph

Joshua Wiley jwiley.psych at gmail.com
Mon Jan 10 03:16:32 CET 2011

Hi Jim,

Some example data would help us.  I typically think of a histogram as
the frequency of values falling within a certain range (determined by
bins).  Since they are univariate plots, I'm not sure how you are
planning on adding a line graph to that.  If you just want bars of the
average gasoline price at different years, perhaps something along
these lines would work for you:

## Load required packages

## Sample Data
dat <- data.frame(year = 1996:2010,
  x1 = rnorm(15, 3, .2), x2 = rnorm(15, 200, 1))

## Base xyplot (not a histogram) adding a layer with different y axis
xyplot(x1 ~ year, data = dat, type = "h") +
  as.layer(xyplot(x2 ~ year, data = dat, type = "l", col = "black"),
  y.same = FALSE)

## See
?hist # for info about histograms



On Sun, Jan 9, 2011 at 5:13 PM, Jim Burke <j.burke at earthlink.net> wrote:
> Hello everyone,
> I have a simple histogram of gasoline prices going back a few years that I
> want to insert a line graph of consumer price index (cpi) over the
> histogram.  I have looked through the "Lattice" book by Deepayan Sarkar but
> don't see anything there. How might this be done? An example would be
> wonderful.
> Current code snippet follows. For example additional field to add as a line
> graph would be a cpi calculation like "gas_data$regular * (2010_cpi /
> gas_data$year )".
> xyplot( regular ~ as.Date(gas_data$dates,"%b %d, %Y") , data = gas_data,
>       type = c("g", "h" ))
> Thanks,
> Jim Burke
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Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles

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