R help - Dec 2003 - diagnostic information in glm. How about N of missing observations?

I handed out some results from glm() and the students ask "how many 
observations were dropped due to missing values"?

How would I know? 

In other stat programs, the results will typically include N and the 
number dropped because of missings.  Without going back to R and 
fiddling about to find the total number of rows in the dataframe, there 
is no way to tell.  Somewhat inconvenient. Do you agree?

-- 
Paul E. Johnson                       email: pauljohn at ku.edu
Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
1541 Lilac Lane, Rm 504                              
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66044-3177           FAX: (785) 864-5700

There should be an element of the fitted model object called `na.action' 
which (if you used the default na.omit()) should tell you which 
observations were dropped.

-roger

Paul Johnson wrote:
> I handed out some results from glm() and the students ask "how many 
> observations were dropped due to missing values"?
> 
> How would I know?
> In other stat programs, the results will typically include N and the 
> number dropped because of missings.  Without going back to R and 
> fiddling about to find the total number of rows in the dataframe, there 
> is no way to tell.  Somewhat inconvenient. Do you agree?
>

Check out

   ?summary.formula

in package Hmisc.

---
Date: Thu, 18 Dec 2003 13:27:39 -0600 
From: Paul Johnson <pauljohn at ku.edu>
To: 'r-help at stat.math.ethz.ch' <r-help at stat.math.ethz.ch> 
Subject: [R] diagnostic information in glm. How about N of missing observations?

 
 
I handed out some results from glm() and the students ask "how many 
observations were dropped due to missing values"?

How would I know? 

In other stat programs, the results will typically include N and the 
number dropped because of missings. Without going back to R and 
fiddling about to find the total number of rows in the dataframe, there 
is no way to tell. Somewhat inconvenient. Do you agree?

-- 
Paul E. Johnson email: pauljohn at ku.edu
Dept. of Political Science http://lark.cc.ku.edu/~pauljohn
1541 Lilac Lane, Rm 504 
University of Kansas Office: (785) 864-9086
Lawrence, Kansas 66044-3177 FAX: (785) 864-5700

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On Thu, 18 Dec 2003 13:27:39 -0600
Paul Johnson <pauljohn at ku.edu> wrote:
> I handed out some results from glm() and the students ask "how many 
> observations were dropped due to missing values"?
> 
> How would I know? 
> 
> In other stat programs, the results will typically include N and the 
> number dropped because of missings.  Without going back to R and 
> fiddling about to find the total number of rows in the dataframe, there 
> is no way to tell.  Somewhat inconvenient. Do you agree?
> 
> -- 
> Paul E. Johnson                       email: pauljohn at ku.edu
> Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
> 1541 Lilac Lane, Rm 504                              
> University of Kansas                  Office: (785) 864-9086
> Lawrence, Kansas 66044-3177           FAX: (785) 864-5700
>
Fitting functions in the Design package tell you how many observations
were deleted due to each variable in the model.  They generalize the
na.action component stored in the fit object.

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