[R] plot with 2 y axes

[Greg Snow]

Why do you need the line to overlay the bars?  Which bars are touched by the line is just a quirk of scaling and could easily change with the scales.  All the overlay does is to make it harder to read, why not jut have 2 panels aligned on the x-axis but with the line plot above the bar plot?

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Mario Beolco
> Sent: Tuesday, January 25, 2011 5:31 PM
> To: r-help at r-project.org
> Subject: [R] plot with 2 y axes
> 
> Dear R users,
> 
> apologies for the total beginner's question. I would like to create a
> barchart for some temperature values with the y axis on the right hand
> side of the plot. On this plot would like to overlay some time series
> data  (in the form of a line) for some other variable called Index.
> The y axis for this latter variable should be on the left hand side of
> the plot.
> 
> An example of what I would like to obtain:
> 
> https://sites.google.com/site/graphtests1/
> 
> I have tried to do this using ggplot2 and this where I have got (for
> data see at the bottom of the e-mail):
> 
> none<-theme_blank()
> p<-ggplot(tmp3,aes(x=year,y=Temperature))
> p1<-p+geom_bar(stat="identity",fill="#9ACD32",colour="#000000")
> p1 + geom_line(data=tmp3, aes(x=year, y=Index),
> colour="black",size=1)+opts(legend.position="none",panel.grid.major=non
> e,panel.grid.minor=none)+opts(panel.border=none)+theme_bw(base_size=20)
> 
> This code does not do what I want because the Temperature y axis
> should be on the left hand side and the the y axis for the other
> variable called Index is not even there (should in theory be on the
> left hand side). I also get the following warning message when I run
> that code "I get Warning message:Stacking not well defined when ymin
> != 0". (Should I worry about this?).
> 
> I do not know whether ggplot2 can is the best package for creating the
> type of plot that I want. I would, however, be very grateful for any
> suggestions on to improve the above code or on how I could use other
> packages to create the plot I want.
> 
> thanks!
> 
> Mario
> 
> 
> 
> "year","Temperature","Index"
> 1966,2.9,1
> 1967,4.5,1.24
> 1968,1.9,1.46
> 1969,1,1.37
> 1970,2.9,1.87
> 1971,4.3,2.66
> 1972,3.9,3.07
> 1973,4.3,3.91
> 1974,4.9,4.16
> 1975,4.4,4.32
> 1976,4.5,2.52
> 1977,2,2.44
> 1978,2.8,2.18
> 1979,-0.4,1.18
> 1980,2.3,1.93
> 1981,3,2.13
> 1982,0.3,1.92
> 1983,1.7,2.24
> 1984,3.3,2.01
> 1985,0.8,1.89
> 1986,-1.1,0.66
> 1987,0.8,1.01
> 1988,4.9,1.5
> 1989,5.2,2.11
> 1990,4.9,2.02
> 1991,1.5,0.7
> 1992,3.7,0.75
> 1993,3.6,1.28
> 1994,3.2,1.37
> 1995,4.8,2.01
> 1996,2.3,1.54
> 1997,2.5,2
> 1998,5.2,2.07
> 1999,5.3,2.11
> 2000,4.9,2.42
> 2001,3.2,2.29
> 2002,3.6,2.15
> 2003,3.9,2.21
> 2004,4.8,2.14
> 2005,4.3,2.33
> 2006,3.7,1.89
> 2007,5.8,2.03
> 2008,4.9,2.58
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.