[R] fitted.values less than observed values

Federico Calboli f.calboli at imperial.ac.uk
Tue Aug 4 19:37:15 CEST 2009

On 4 Aug 2009, at 18:27, David Winsemius wrote:

> Your first posting made me think that you were complaining that the
> fitted values were less than the raw values. Your second posting makes
> me think that you may be conflating the English word "less" with  the
> word English "fewer". Many native speakers make the same error, but in
> this context it may be a critical problem for communicating what you
> are seeing (or not seeing).
> Perhaps you could be more expansive about what you see and what you
> expect with explicit attention to the numbers involved? Even better
> would be small *reproducible* example.

Problem solved, I realised there are NAs in the data which I had  
completely forgot about (serves me right for digging up old data to  
add results to a paper). Without any irony or sarcasm, thanks for the  
grammar correction, it might prove useful in the future.



> -- 
> David
> On Aug 4, 2009, at 12:51 PM, Federico Calboli wrote:
>> Actually, I tried doing
>> data2 = unique(data)
>> mod = lm(y ~ x1 + ... + xn, data2)
>> fitted(mod)
>> and I still get les fitted values than observations.
>> Federico
>> On 4 Aug 2009, at 12:18, Federico Calboli wrote:
>>> Hi All,
>>> I have some data where the dependent variable is a score, low (1:3)
>>> or
>>> high (8:9), and the independent variables are 21 genotypic markers.
>>> I'm fitting a logistic regression on the whole dataset after
>>> transforming the score to 0/1 and normal linear regression on the
>>> high
>>> and low subsets.
>>> I all cases I have a numer of cases of data 'duplications', i.e.
>>> different individuals with the same score and the same genotype at
>>> the
>>> 21 markers.
>>> When I do:
>>> mod$fitted.values I get a number of fitted values corresponding to
>>> the
>>> umber of unique lines in the dataset. Is there a way to have the
>>> fitted  values match the observation, even though some are  
>>> duplicated
>>> and so have the same fitted value? I could do it by hand but it's
>>> laborious and I'd venture there is a better way.
>>> Best,
>>> Federico
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT

Federico C. F. Calboli
Department of Epidemiology and Public Health
Imperial College, St. Mary's Campus
Norfolk Place, London W2 1PG

Tel +44 (0)20 75941602   Fax +44 (0)20 75943193

f.calboli [.a.t] imperial.ac.uk
f.calboli [.a.t] gmail.com

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