R help - Sep 2010 - how can I plot bar plots with all the bars (negative and positive) in the same direction????

Dear r-help mailing list,

this seems stupid, but I actually don't find the solution:

if I have a vector of numbers x of length n, ranging, say, from -3 to 4, if I do

barplot (x)

all the values below 0 go downwards, and all the positive values go upward. How
can I make them all begin from the minimum pointing upwards?

Thanks!


Gabriele Zoppoli, MD
Ph.D. Fellow, Experimental and Clinical Oncology and Hematology, University of
Genova, Genova, Italy
Guest Researcher, LMP, NCI, NIH, Bethesda MD

Work: 301-451-8575
Mobile: 301-204-5642
Email: zoppolig at mail.nih.gov

In the bar plot, the vertical axis is a numerical axis representing the
frequency (the height of the vertival bar -= frequency). If you really want
to have vertical bar corresponding to the negative values go downward, you
need to make your own function to achieve the goal.
-- 
View this message in context:
http://r.789695.n4.nabble.com/how-can-I-plot-bar-plots-with-all-the-bars-negative-and-positive-in-the-same-direction-tp2526006p2526021.html
Sent from the R help mailing list archive at Nabble.com.

Dear Gabriele,

I suspect the reason you are having difficulty finding the solution is
because barplots were meant to be anchored at 0.

What information are you really trying to convey?  There is probably a
very clear, aesthetically pleasing way to achieve your goal without a
barplot.

For instance, what about a simple scatter plot?

dat <- (-3:4)
plot(x = 1:length(dat), y = dat, xaxt = "n", xlab = "My
Groups")
axis(side = 1, at = 1:length(dat), labels = LETTERS[1:8])

Alternately, you could add the minimum to your data so it started at 0...

barplot(dat + abs(min(dat)))

Hadley will never forgive me for mentioning this but, if you have a
desperate need to use bars that are anchored at the minimum value, you
could use geom_rect() in package ggplot2...

mydf <- data.frame(x = 1:8, y = dat)
library(ggplot2)
ggplot(mydf, aes(xmin = x, xmax = x + 1, ymin = min(y), ymax = y)) + geom_rect()

HTH,

Josh

On Fri, Sep 3, 2010 at 10:12 AM, Zoppoli, Gabriele (NIH/NCI) [G]
<zoppolig at mail.nih.gov> wrote:
> Dear r-help mailing list,
>
> this seems stupid, but I actually don't find the solution:
>
> if I have a vector of numbers x of length n, ranging, say, from -3 to 4, if
I do
>
> barplot (x)
>
> all the values below 0 go downwards, and all the positive values go upward.
How can I make them all begin from the minimum pointing upwards?
>
> Thanks!
>
>
> Gabriele Zoppoli, MD
> Ph.D. Fellow, Experimental and Clinical Oncology and Hematology, University
of Genova, Genova, Italy
> Guest Researcher, LMP, NCI, NIH, Bethesda MD
>
> Work: 301-451-8575
> Mobile: 301-204-5642
> Email: zoppolig at mail.nih.gov
> ______________________________________________
> 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.
>


-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/

On Sep 3, 2010, at 1:12 PM, Zoppoli, Gabriele (NIH/NCI) [G] wrote:
> Dear r-help mailing list,
>
> this seems stupid, but I actually don't find the solution:
>
> if I have a vector of numbers x of length n, ranging, say, from -3  
> to 4, if I do
>
> barplot (x)
>
> all the values below 0 go downwards, and all the positive values go  
> upward. How can I make them all begin from the minimum pointing  
> upwards?
>
 > grp.n <-c(0, -1, -2, -3, -5, -1,  3, -2,  2,  0)
 > barplot(grp.n-min(grp.n), axes=FALSE)
 > axis(2, grp.n-min(grp.n), labels=as.character(grp.n))


Compare
 > barplot(grp.n, axes=FALSE)


-- 
David Winsemius, MD
West Hartford, CT

On 03-Sep-10 17:12:55, Zoppoli, Gabriele (NIH/NCI) [G]
wrote:
> Dear r-help mailing list,
> 
> this seems stupid, but I actually don't find the solution:
> 
> if I have a vector of numbers x of length n, ranging, say,
> from -3 to 4, if I do
> 
> barplot (x)
> 
> all the values below 0 go downwards, and all the positive values go
> upward. How can I make them all begin from the minimum pointing
> upwards?
> 
> Thanks!
> Gabriele Zoppoli, MD
It's not completely clear what you want to see, given the vector.
However, the reason you are seeing the bars go upwards and
downwards is given at the beginning of '?barplot':

  barplot(height, width = 1, space = NULL, ... )

Therefore, if x is a vector of positive and negative numbers,
barplot(x) will correctly draw bars with negative heightslues 
(downwards) at negative values of x, and with positive heights
(upwards) for positive values of x.

On the other hand, possibly you want to see a barplot which
corresponds to a histogram, i.e. for each distinct value of x
you get a bar pointing upwards with height equal to the count
of that value.

For example:

  set.seed(54321)
  x<-sample(((-3):4),100,replace=TRUE)
  x  ### Have a look at the values in x
  barplot(x)  ### A barplot with bar heights given by x
  barplot(table(x))  ### a barplot of the counts of the values of x

Hoping this helps,
Ted.



--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 03-Sep-10                                       Time: 19:08:34
------------------------------ XFMail ------------------------------

As is often the case in R, just because you shouldn't do something,
doesn't
mean you can't do it.  Still, I'd urge you to consider the "visual
honesty"
of what you propose.

If you're still insistent:
dat <- (-3:4)
dat1=dat-min(dat)
barplot(dat1,axes=FALSE)
axis(2,dat1,labels=dat)

Typically, zero is a reference point and/or the identity element for 
addition.  Your plot audience will interpret it this way.  If you want to 
look at difference scores from the minimal value, shouldn't that be exactly 
how you label your y-axis, and not with the pre-transformed numbers?

Are you still sure you don't like the default behavior?

Rob Baer


----- Original Message ----- 
From: "Zoppoli, Gabriele (NIH/NCI) [G]" <zoppolig at
mail.nih.gov>
To: <r-help at r-project.org>
Sent: Friday, September 03, 2010 12:12 PM
Subject: [R] how can I plot bar plots with all the bars (negative and 
positive) in the same direction????

> Dear r-help mailing list,
>
> this seems stupid, but I actually don't find the solution:
>
> if I have a vector of numbers x of length n, ranging, say, from -3 to 4, 
> if I do
>
> barplot (x)
>
> all the values below 0 go downwards, and all the positive values go 
> upward. How can I make them all begin from the minimum pointing upwards?
>
> Thanks!
>
>
> Gabriele Zoppoli, MD
> Ph.D. Fellow, Experimental and Clinical Oncology and Hematology, 
> University of Genova, Genova, Italy
> Guest Researcher, LMP, NCI, NIH, Bethesda MD
>
> Work: 301-451-8575
> Mobile: 301-204-5642
> Email: zoppolig at mail.nih.gov
> ______________________________________________
> 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.
>

I believe that you will have to draw them in ggplot2 as someone mentioned or in
base graphics.  Here is a rough first attempt that may give you some ideas.
===============================xx <- -3:4
yy <- rep(-3,length(xx))
plot(xx,xx,  type="n", xlim=c(-4, 5))
rect(xx, yy, xx+.5, xx )
===============================
--- On Fri, 9/3/10, Zoppoli, Gabriele (NIH/NCI) [G] <zoppolig at
mail.nih.gov> wrote:
> From: Zoppoli, Gabriele (NIH/NCI) [G] <zoppolig at mail.nih.gov>
> Subject: [R] how can I plot bar plots with all the bars (negative and
positive) in the same direction????
> To: "r-help at r-project.org" <r-help at r-project.org>
> Received: Friday, September 3, 2010, 1:12 PM
> Dear r-help mailing list,
> 
> this seems stupid, but I actually don't find the solution:
> 
> if I have a vector of numbers x of length n, ranging, say,
> from -3 to 4, if I do
> 
> barplot (x)
> 
> all the values below 0 go downwards, and all the positive
> values go upward. How can I make them all begin from the
> minimum pointing upwards?
> 
> Thanks!
> 
> 
> Gabriele Zoppoli, MD
> Ph.D. Fellow, Experimental and Clinical Oncology and
> Hematology, University of Genova, Genova, Italy
> Guest Researcher, LMP, NCI, NIH, Bethesda MD
> 
> Work: 301-451-8575
> Mobile: 301-204-5642
> Email: zoppolig at mail.nih.gov
> ______________________________________________
> 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.
>