R help - Mar 1999 - Can't understand error message :-{

I'm sorry if this is a basic question, but I'm stumped. I'm just
trying to plot
the residuals from a linear model against another variable in the data frame.
Here are the lines I'm trying to execute:

size <-
read.table(file="/u67/abasl70/surveys/annenberg/mega/smschl.dat",
header=T)
sizef <- data.frame(size, row.names=size$unit)
attach(sizef)
mschmod <- lm (mavgres ~ crimesch + socstat + povnojob + ploinc94 + aa94 +
hisp94 + minty94 + mixed94, data=sizef)
plot(mschmod$residuals ~ size94)

The last line gives this error message:
Error in model.frame(formula, rownames, variables, varnames, extras,
extranames,  : variable lengths differ

In fact, the lengths are different:
> length(mschmod$residuals)
[1] 379
> length(size94)
[1] 384

but I'm sure I don't know 1) how this happened since it all came from
the same
data frame, or 2) why it should prevent me from plotting the data. If someone
can tell me how to fix this (before I have to present the results at this
Thursday's meeting!) I'd be very appreciative. 
______________________________________________________________________
Stuart Luppescu         -=-=-  University of Chicago
ºÍʸ ¤ÈÃÒÆàÈþ¤ÎÉã(EUC)  -=-=-  s-luppescu at uchicago.edu
http://www.consortium-chicago.org/people/sl/sl.html
ICQ #21172047  AIM: psycho7070
Bare feet magnetize sharp metal objects so they point upward from the
floor -- especially in the dark.
>> Sent on 02-Mar-99 at 10:00:07 with xfmail
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Stuart Luppescu <s-luppescu at uchicago.edu> writes:
> attach(sizef)
> mschmod <- lm (mavgres ~ crimesch + socstat + povnojob + ploinc94 + aa94
+
> hisp94 + minty94 + mixed94, data=sizef)
> plot(mschmod$residuals ~ size94)
> 
> The last line gives this error message:
> Error in model.frame(formula, rownames, variables, varnames, extras,
> extranames,  : variable lengths differ
> 
> In fact, the lengths are different:
> > length(mschmod$residuals)
> [1] 379
> > length(size94)
> [1] 384
> 
> but I'm sure I don't know 1) how this happened since it all came
from the same
> data frame, or 2) why it should prevent me from plotting the data. If
someone
> can tell me how to fix this (before I have to present the results at this
> Thursday's meeting!) I'd be very appreciative. 
(1) Missing values in response and/or regressors cause cases to be
    discarded. 
(2) Plotting which of the y's against which x's ?

plot(mschmod$residuals ~ size94[complete.cases(mavgres,crimesch,
socstat,povnojob,ploinc94,aa94,hisp94,minty94,mixed94)])

should do the trick. Or, simpler but sneakier:

attach(sizef[rownames(mschmod$model),])
plot(residuals(mschmod) ~ size94)
detach()

It should also work with:

evalq(plot(residuals(mschmod) ~ size94), sizef[rownames(mschmod$model),])

(none of the above is tested, since I don't have your data of course)
-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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