[R] Modifying dataframe with mutate()

[Patrick (Malone Quantitative)]

Jeff,

mutate(), which is I think part of dplyr, also violates this, for what it's
worth. I suspect the breaking point is that mutate() is intended to create
new columns in the dataframe, not alter existing ones.

On Sat, Jul 25, 2020 at 3:52 PM Jeff Newmiller <jdnewmil using dcn.davis.ca.us>
wrote:

> R is largely a functional language. You do something to an input and end
> up with an output that has no effect on the input. This is actually a
> highly desirable feature.
>
> If you want your df variable to reflect changes made then you  need to
> assign your result back into it.
>
> df <- df %>% mutate(v1 = as.double(v1))
>
> (Note that the data.table package violates this principle and is
> controversial as a result.)
>
> On July 25, 2020 12:11:24 PM PDT, H <agents using meddatainc.com> wrote:
> >In a statement like:
> >
> >df %>% mutate(v1 = as.double(v1))
> >
> >I expect the variable v1 in dataframe df to have been converted into a
> >double. However, when I do:
> >
> >str(df)
> >
> >v1 still shows as int. Do I need to save the modified dataframe after
> >mutating a variable?
> >
> >______________________________________________
> >R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >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.
>
> --
> Sent from my phone. Please excuse my brevity.
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>


-- 
Patrick S. Malone, Ph.D., Malone Quantitative
NEW Service Models: http://malonequantitative.com

He/Him/His

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