R help - Sep 2009 - Very basic question regarding plot.Design...

Hello ALL!
I have a problem to plot factor (lets say gender) as a line, or at least 
both line and point, from ols model:
ols1 <- ols(Y ~ gender, data=dat, x=T, y=T)
plot(ols1, gender=NA, xlab="gender", ylab="Y",
ylim=c(5,30), conf.int=FALSE)

If I convert gender into discrete numeric predictor, and use 
forceLines=TRUE, plot is not nice and true, since it shows values 
between 1 and 2.

Thanks!
PM

Petar Milin wrote:
> Hello ALL!
> I have a problem to plot factor (lets say gender) as a line, or at least 
> both line and point, from ols model:
> ols1 <- ols(Y ~ gender, data=dat, x=T, y=T)
> plot(ols1, gender=NA, xlab="gender", ylab="Y",
> ylim=c(5,30), conf.int=FALSE)
> 
> If I convert gender into discrete numeric predictor, and use 
> forceLines=TRUE, plot is not nice and true, since it shows values 
> between 1 and 2.
> 
> Thanks!
> PM
> 
Petar,

forceLines seems to be doing what it was intended to do.  I'm not clear 
on why you need a line, though.  If you provide self-contained code and 
data that replicate your problem I may be able to help more, or you can 
try a new package I'm about to announce.

Frank
-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University

Petar Milin wrote:
> I would like to have a line on this plot, instead of two points:
> 
> x1 = rnorm(100, 10, 2.5)
> x2 = rnorm(100, 26, 3.2)
> x1 = as.data.frame(x1)
> x2 = as.data.frame(x2)
> colnames(x1) = 'anxiety'
> colnames(x2) = 'anxiety'
> x1$gender = 'male'
> x2$gender = 'female'
> dat = rbind(x1, x2)
> 
> require(Design)
> 
> attach(dat)
> d=datadist(gender)
> options(datadist="d")
> 
> ols1 <- ols(anxiety ~ gender, data=dat, x=T, y=T)
> 
> plot(ols1, gender=NA, xlab="gender", ylab="anxiety",
> ylim=c(5,30), conf.int=FALSE)
> 
> detach(dat)
Your code has many problems and inefficiencies in it.  Here are some 
suggested fixes and the commands needed using the new rms package:

require(rms)
n <- 100
anxiety <- c(rnorm(n, 10, 2.5), rnorm(n, 26, 3.2))
gender  <- c(rep('male', n), rep('female',n))
d <- datadist(gender); options(datadist='d')
f <- ols(anxiety ~ gender)
p <- Predict(f, gender=.)
# For this case could also do p <- Predict(f); plot(p) would give a
# vertical dot chart
p           # print estimates
plot(p)     # horizontal dot chart; preferred for categorical predictors
# To take control using lines:
with(p, plot(1:2, yhat, type='l', xlab='gender numeric'))

Frank
> 
> Thanks!
> PM
> 
> Frank E Harrell Jr wrote:
>> Petar Milin wrote:
>>> Hello ALL!
>>> I have a problem to plot factor (lets say gender) as a line, or at 
>>> least both line and point, from ols model:
>>> ols1 <- ols(Y ~ gender, data=dat, x=T, y=T)
>>> plot(ols1, gender=NA, xlab="gender", ylab="Y",
>>> ylim=c(5,30), conf.int=FALSE)
>>>
>>> If I convert gender into discrete numeric predictor, and use 
>>> forceLines=TRUE, plot is not nice and true, since it shows values 
>>> between 1 and 2.
>>>
>>> Thanks!
>>> PM
>>>
>>
>> Petar,
>>
>> forceLines seems to be doing what it was intended to do.  I'm not 
>> clear on why you need a line, though.  If you provide self-contained 
>> code and data that replicate your problem I may be able to help more, 
>> or you can try a new package I'm about to announce.
>>
>> Frank
> 

-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University