r - Is there a reason to prefer extractor functions to accessing attributes with $? -

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on thread on crossvalidated, made following comment:

i suspect r question difference between working s3 classes (that accessed via $) & s4 classes (that accessed via @)...

@gavin simpson subsequently commented:

@gung more spot on, solution not delve objects , rip out whatever feel learn use extractor functions, in case coefficients() or shorter alias coef(), in coef(fit)

i'm intrigued this. why using coef(model) be better than model$coefficients[,1], example? (i recognize latter uglier , requires more typing, doubt that's reason intended.) case there isn't existing extractor function (e.g., accessing t-statistics)?

because author of package using free change underlying structure of model object without worrying breaking everyone's code.

obviously generalizes r core well. recommended use extractor functions because can sure return correct information, if function authors find necessary shuffle things around under hood.

maybe add more information 1 of elements of model list object, , changes order of everything? code break.


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