That worked!  Thank you very much for the help. 
 
I think I have one last question about qplot in ggplot2, That is exporting the plot to JPG while in a loop.   I tried what was recommended in "Re: [R] jpeg() creating empty files with qplot() in a loop", however, I received some errors (see below).  I also tried using a PDF, but that did not work either, i.e. the PDF produced was blank.  Oddly enough the results produced using "dev.print(file="qplot_output.jpg", device=jpeg, width=600) " in a loop are blank, i.e. the JPG file is there, but it is blank.  Unfortunately,  "ggsave(file="ggsave_qplot_output.jpg")" does not even produce a JPG file output.  Any help at this point is greatly appreciated.  Is the problem related to the fact that I need to use the plain "hist" and "dev.print" prior to using ggplot's qplot? 
 
Thanks again for all your help.   

 
> for(jj in 0:4)
+ {
+   rnorm_test_data<-rnorm(1000,3,6)
+   hist(rnorm_test_data)
+   dev.print(file="test_data.jpg", device=jpeg, width=600) 
+ 
+   plot.new()  
+   qplot(rnorm_test_data, geom = "histogram", binwidth = 1) + 
+         scale_x_continuous("Test Data") + scale_y_continuous("Frequency") + 
+         scale_fill_discrete("qplot histogram")
+   
+   # Print the plot to a JPG or PDF 
+   dev.print(file="qplot_output.jpg", device=jpeg, width=600)   
+   ggsave(file="ggsave_qplot_output.jpg") 
+   ggsave(file = "ggsave_qplot_output.pdf")
+ 
+ }      
Saving 6.9" x 6.89" image
Error in get(as.character(FUN), mode = "function", envir = envir) : 
  variable "jpg" of mode "function" was not found
> 

 

 
 
g 6.9" x 6.89" image
Error in get(as.character(FUN), mode = "function", envir = envir) : 
  variable "jpg" of mode "function" was not found
 
P.S. Here is the 
> sessionInfo()
R version 2.8.0 (2008-10-20) 
i386-pc-mingw32 
locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United States.1252;LC_MONETARY=English_United States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods   base     
other attached packages:
 [1] ggplot2_0.8.1      reshape_0.8.2      RColorBrewer_1.0-2 proto_0.3-8        plyr_0.1.4         nortest_1.0        fBasics_280.74     timeSeries_290.79 
 [9] timeDate_290.81    vcd_1.2-1          MASS_7.2-44        colorspace_1.0-0  


--- On Tue, 1/6/09, ONKELINX, Thierry <Thierry.ONKELINX@inbo.be> wrote:

From: ONKELINX, Thierry <Thierry.ONKELINX@inbo.be>
Subject: RE: [R] R Stacked Histogram
To: jasonkrupert@yahoo.com, r-help@r-project.org
Date: Tuesday, January 6, 2009, 9:54 AM

Dear Jason,

Have a look at scale_y_continuous() and scale_fill_discrete(). This might work
(untested as your example is not reproducible with a (dummy) dataset).

qplot(Age, data = recerts_combined_values, binwidth = 5, fill =
combined_values$Test.Type, main="Combined Age Histogram") +
scale_x_continuous("Age, months") +
scale_y_continuous("Counts") + scale_fill_discrete("Type of
Tests")

HTH,

Thierry


----------------------------------------------------------------------------
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics, methodology
and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium 
tel. + 32 54/436 185
Thierry.Onkelinx@inbo.be 
www.inbo.be 

To call in the statistician after the experiment is done may be no more than
asking him to perform a post-mortem examination: he may be able to say what the
experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not ensure
that a reasonable answer can be extracted from a given body of data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-help-bounces@r-project.org [mailto:r-help-bounces@r-project.org] Namens
Jason Rupert
Verzonden: dinsdag 6 januari 2009 16:00
Aan: r-help@r-project.org
Onderwerp: Re: [R] R Stacked Histogram

Great advice.  I did a quick read and came up with the following:
 
qplot(Age, data = recerts_combined_values, binwidth = 5, 
         fill = combined_values$Test.Type, 
         ylab="Counts", xlab="Age, months",  
         main="Combined Age Histogram", 
         legend.name = "Type of Tests")

Unfortunatley, here is a description of the results:
(1) the "main" title font size by default is too large and is clipped
by the image (guess I need to figure out how to fix this), 
(2) ylab appears to fail - it does not replace the default "count"
label - what should I do to fix this?
(3) like (2), neither using "legend.name" nor
"legend.title" appears to replace/change the name of the legend
title/name.  
 
By any chance can you provide some advice for tackeling these items?  These
are probably due to me being a noobie on the ggplot2 package.  
 
Thanks again.
 

--- On Mon, 1/5/09, hadley wickham <h.wickham@gmail.com> wrote:

From: hadley wickham <h.wickham@gmail.com>
Subject: Re: [R] R Stacked Histogram

Cc: r-help@r-project.org
Date: Monday, January 5, 2009, 7:42 AM


wrote:
> Understood.  Will head the warning about odd way to display data.
>
> Any recommendations about where I look to find full details about
"qplot".
>
> I tried ?qplot, but it did not return full details.
>
> That description was missing a few items, e.g. fill, which is used below.

The best place to start is the qplot chapter of the ggplot2 book -
http://had.co.nz/ggplot2/book

Regards,

Hadley

-- 
http://had.co.nz/



      
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