Why can't Anove (car package) see the data?

Dear Patrick,

It's difficult for me to tell from your description what the specific
nature of the problem is, though it seems to be some kind of scoping issue.

I've experimented a bit and found that the call to update (indirectly) from
Anova.glm (with LR type-II tests) seems to cause problems:

     > fun.1 <- function(df){

     +     mod <- glm(partic != 'not.work' ~ hincome + children + region,
     +         data=df, family=binomial)
     +     Anova(mod)
     +     }

     > fun.1(Womenlf)

     Error in eval(expr, envir, enclos) : numeric envir arg not of length one

     > traceback()

     16: eval(predvars, data, env)
     15: model.frame.default(formula = partic != "not.work" ~ children +
             region, data = df, drop.unused.levels = TRUE)
     14: model.frame(formula = partic != "not.work" ~ children + region,
             data = df, drop.unused.levels = TRUE)
     13: eval(expr, envir, enclos)
     12: eval(mf, parent.frame())
     11: glm(formula = partic != "not.work" ~ children + region, family =
binomial,
             data = df)
     10: eval(expr, envir, enclos)
     9: eval(call, parent.frame())
     8: update.default(mod, eval(parse(text = paste(".~.-",
paste(c(names[term],
         rels), collapse = "-")))))
     7: update(mod, eval(parse(text = paste(".~.-", paste(c(names[term],
         rels), collapse = "-")))))
     6: Anova.II.LR.glm(mod)
     5: switch(test.statistic, LR = Anova.II.LR.glm(mod), Wald =
Anova.II.Wald.glm(mod),
         F = Anova.II.F.glm(mod, error, error.estimate))
     4: switch(type, II = switch(test.statistic, LR = Anova.II.LR.glm(mod),
         Wald = Anova.II.Wald.glm(mod), F = Anova.II.F.glm(mod, error,
             error.estimate)), III = switch(test.statistic, LR =
Anova.III.LR.glm(mod),
         Wald = Anova.III.Wald.glm(mod), F = Anova.III.F.glm(mod,
             error, error.estimate)))
     3: Anova.glm(mod)
     2: Anova(mod)
     1: fun.1(Womenlf)

(This uses the Womenlf data frame in the car package.)

In contrast, Anova.lm, which doesn't call update, works OK:

    > fun.2 <- function(df){

     +     mod <- lm(prestige ~ income + education, data=df)
     +     Anova(mod)
     +     }

     > fun.2(Prestige)

     Anova Table (Type II tests)

     Response: prestige
             Sum Sq Df F value    Pr(>F)
     income    2248.1  1  36.856 2.355e-08
     education 8577.3  1 140.615 < 2.2e-16
     Residuals 6038.9 99

     >

(using the Prestige data frame, again in car.)

I don't see an immediate way around the problem, but I'll think about it.
In addition, if you send me some more information -- the data that you were
using, the model that you fit, the function from which you called Anova --
I'll take a look a it. I'm leaving town for several days tomorrow. If you
send me the information before then, I'll take it with me.

I'm sorry that you're experiencing this problem,
  John

At 03:14 PM 8/14/2002 +1200, Patrick Connolly wrote:

At the end of the 'Details:' section of the help on Anova (car
package), it states:

     The standard R `anova' function calculates sequential (type-I)
     tests. These rarely test meaningful hypotheses.

So I thought I'd try it.  However, I was perplexed to get this
message:

Browse[1]> Anova.glm(leaf.glm1, type ="II")
Error in terms.formula(formula, data = data) :
        Object "use.df" not found

The regular anova function can find use.df.  What could make it
invisible to Anova?  I thought it might be because terms.formula took
an argument x and I already had an object x, but changing its name
didn't help.  I spent some time searching the archives but found no
mention of this problem.  I read some of the car package help files,
but didn't notice a reference to what is different in the way data is
seen.

The example given in the help file does work, but it uses a data
object which is in the working directory.  That's not practicable
within a function.  So I'd appreciate other ideas.

platform i686-pc-linux-gnu
arch     i686
os       linux-gnu
system   i686, linux-gnu
status
major    1
minor    5.1
year     2002
month    06
day      17
language R

Thanks

--
Patrick Connolly
HortResearch
Mt Albert
Auckland
New Zealand
Ph: +64-9 815 4200 x 7188
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~
I have the world`s largest collection of seashells. I keep it on all
the beaches of the world ... Perhaps you`ve seen it.  ---Steven Wright
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~

-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
-----------------------------------------------------

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