[R] understanding print.summary.lm and perhaps print/show in general

[Petr Klasterecky]

Another solution is to look into the code of summary.lm a few lines 
above where the (dim)names are assigned. Based on this, you may try

lma <- lm(dist ~ speed, data=cars)
suma <- summary(lma)
colnames(suma$coef) <- c(LETTERS[1:4])
printCoefmat(suma$coef) # prints what I expect
suma

dimnames(suma$coefficients) <- list(names(suma$coefficients), 
c(LETTERS[1:4]))
suma

You might also find reading the chapter on generic functions in the 
R-lang (R language definition) manual useful.
Petr

Christos Hatzis napsal(a):
> Paul,
> 
> Usually summary methods perform some computations if needed and then change
> the class of the original object so that a print method can be called for
> the new summary object.
> 
> In this case, this is done at the end of the summary.lm method:
> 
> ...
>     if (!is.null(z$na.action)) 
>         ans$na.action <- z$na.action
>     class(ans) <- "summary.lm"
>     ^^^^^^^^^^^^^^^^^^^^^^^^^^
>     ans
> }
> 
> So then print.summary.lm does all the job displaying the summary.lm object.
> To see that function do
> 
> getAnywhere(print.summary.lm)
> 
> Then you can then modify that function as needed.
> 
> -Christos
> 
> Christos Hatzis, Ph.D.
> Nuvera Biosciences, Inc.
> 400 West Cummings Park
> Suite 5350
> Woburn, MA 01801
> Tel: 781-938-3830
> www.nuverabio.com
>  
> 
> 
>> -----Original Message-----
>> From: r-help-bounces at stat.math.ethz.ch 
>> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Paul Bailey
>> Sent: Friday, March 09, 2007 9:34 AM
>> To: r-help at stat.math.ethz.ch
>> Subject: [R] understanding print.summary.lm and perhaps 
>> print/show in general
>>
>> I'm trying to understand how R prints summary.lm objects and 
>> trying to change it slightly for a summary function that 
>> calculates standard errors using an alternative method.
>>
>> I've found that I can modify a summary.lm object and then it 
>> prints the modified way but I want to change a few things in 
>> the print method that I think I might just be able to do. One 
>> is that I want the coefficients table to print a different 
>> header (other than "Std. Error"). I've tried changing the 
>> column name of the summary$coef matrix and this works for 
>> calls to printCoefmat but it still prints out "Std. Error"
>> when I pass  the summary.lm to the command line by itself. I 
>> don't understand this behavior. When I do this (enter an 
>> object on the command line by itself), does it then calls the 
>> print / show method associated with that objects class, in 
>> this case, summary.lm? Below is some sample code to reproduce 
>> the behavior I don't understand and a comment regarding the 
>> result I don't understand.
>>
>> Cheers,
>> Paul
>>
>> #####
>> lma <- lm(dist ~ speed, data=cars)
>> suma <- summary(lma)
>> colnames(suma$coef) <- c(LETTERS[1:4])
>> printCoefmat(suma$coef) # prints what I expect suma # the 
>> above is the print behavior question regards, # why does the 
>> coefficients matrix have in its header # the usual "Estimate 
>> Std. Error t value Pr(>|t|)"
>> # I expect "A B C D" as above in the call to printCoefmat
>>
>> ______________________________________________
>> R-help at stat.math.ethz.ch mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide 
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 

-- 
Petr Klasterecky
Dept. of Probability and Statistics
Charles University in Prague
Czech Republic