On Mon, 22 Jun 2009, charles78 wrote:
It is not the case as you described. In any case, the total area should be 1
and labeled fraction on y axis should be far less than 1, since I have more
than 10000 data points. I also test differerent bin size by change the
break.
Try reading Greg's response again. Then calculate the area of one of the bars
in your histogram, remembering that the area of a rectangle is not the same as
its height, but is the width times height. If the area of the bar is greater than
1, then you can report a problem.
-thomas
I draw the graph using only 1 group, the same result was obtained.
Any othe suggestion?
Charles.
Greg Snow-2 wrote:
When freq=FALSE then the y axis is not the proportion in each group (what
I am assuming you mean by fraction), but rather is scaled so that the
total area of the histogram is 1 (making comparing to theoretical
densities easier). If all the data values are between 0 and 1, then the
height of at least one bar needs to be >= 1 for the total area to equal 1.
If you want the y-axis to show relative frequency (proportion, fraction,
etc.), then you either need to plot the y-axis yourself or use a different
function than 'hist'.
--
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.s...@imail.org
801.408.8111
-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-
project.org] On Behalf Of charles78
Sent: Monday, June 22, 2009 10:08 AM
To: r-help@r-project.org
Subject: [R] Help needed: Fraction for Histogram > 1 ???
I have been trying to draw histogram for my manscript and found some
strange
things that I could not figure out why.
Using the same code listed below I have successfully draw histograms
for a
few figures with fraction labeled on Y axis less than 1 (acturally
between 0
to 0.1). But one dataset gives the Y axis label 0 to 5 as fraction.
This
is not true, as fraction are less than 1, although the value
distribution on
the figure seems to me is right.
The only difference between the first few datasets and last dataset is:
All values for the first few data sets > 1.
The values for the last data sets between 0 and <1.
Any idea why this happens.
Your help is highly appreciated.
Charles
=================================================
==
postscript("Figure.eps", paper="letter", horizontal=FALSE)
par(mfrow=c(3,3))
par(omi=c(2,0.2,1.8,0.2), mai=c(0.4, 0.4, 0.5, 0.1) )
my.input <- read.table("input.data", header=FALSE, sep="\t")
my.input.exp <- read.table("exp.data", header=FALSE, sep="\t")
hist(my.input.exp[,2], breaks=40,freq = FALSE,xlab="", border =
"grey30",
ylab="", main="")
hist(my.input[,2], breaks=40,freq = FALSE,xlab="", ylab="", main="",
border
= "red",add =TRUE)
mtext("Fraction", side=2, line=2, cex=0.7)
box()
=================================================
=====
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-
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and provide commented, minimal, self-contained, reproducible code.
Thomas Lumley Assoc. Professor, Biostatistics
tlum...@u.washington.edu University of Washington, Seattle
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