On Tue, 27 May 2008, Xiaohui Chen wrote:
Note that the scale of x-axis and y-axis is different in your plot. One
simple way to avoid this is to keep the data unit in the x direction is equal
that in the y direction, by setting asp=1 in calling plot function.
Or when that is not possible or not desirable translate the slope to
the device scales:
usr2dev <- function(x) 180/pi*atan(x * diff( par("usr")[1:2])/
diff(par("usr")[3:4]))
text(2,yval,"Regression", srt=usr2dev( slope ), adj=0)
HTH,
Chuck
X
Dr. Christoph Scherber ??????:
Dear all,
I stumbled over a problem recently when trying to use srt with text() on a
windows device.
What I intended to do was to plot a simple regression line, and to rotate
a piece of text such that the text has the same angle as the regression
line.
However, the text is always plotted in a slightly wrong angle:
####
x=1:10 #create arbitrary x and y values
y=x*2-rnorm(1:10)
plot(x,y,pch=16,xlim=c(0,10)) #create the graph
abline(lm(y~x))
#calculate the y coordinate of the text:
yval=predict(lm(y~x),list(x=rep(2,length(x))))[1]
#calculate the slope:
slope=as.numeric(lm(y~x)[[1]][2])
text(2,yval,"Regression",srt=180/pi*atan(slope),adj=0)
####
What am I doing wrong here?
Many thanks in advance for any help!
Best wishes
Christoph
(using R 2.6.1 on Windows XP)
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:[EMAIL PROTECTED] UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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