[R] Summarizing select columns in a data frame

[Bert Gunter]

There are literally tons of ways to do this sort of thing in R.

In base R ?tapply and friends, especially ?ave and ?by that may be close to
what you want.
But there is a whole parallel universe -- the so-called "tidyverse set of
packages -- that many folks prefer.
This link takes you down that rabbit hole: https://dplyr.tidyverse.org/

There are still others (e.g. the data.table package). You should expect to
invest a little time in learning whichever you choose. You may wish to also
search a bit for tutorials on your choice -- there are many good ones out
there.


Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Sun, Jan 17, 2021 at 12:18 PM Bernard McGarvey <
mcgarvey.bernard using comcast.net> wrote:

> I have a data frame that consists of several factor columns say A, B, C,
> D, and E and several columns containing numerical data, say X1, X2, ....
> X10. I would like to create statistics of some of the numerical columns by
> some of the factor columns. For example,
>
> Calculate the mean, min, and max of variables X1 and X7, by factors A, and
> E. The results should look like the table below:
>
> Factor A Factor E     mean(X1) min(x1) max(X1) mean(X7) min(x7) max(X7)
> mean(X10) min(x10) max(X10)
> A1        E1
> A1        E2
> A1        E3
> A2        E1
> A2        E2
> A2        E3
>
> I would like the results to be returned to a data frame or other object
> that I can write out using the write.csv function. I have looked at the
> summarize and numSummary functions but they do not appear to be flexible
> enough to do the above.
>
> Any help would be appreciated,
>
> Thanks
>
> Bernard McGarvey
> Director, Fort Myers Beach Lions Foundation, Inc.
> Retired (Lilly Engineering Fellow).
>
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