[R] How to use apply() to fill matrix by rows or columns?

C W tmrsg11 at gmail.com
Sat Feb 25 04:37:45 CET 2017


Thanks for letting me know. That line does look familiar.

It's interesting how I simply copy and paste from R editor can result in
HTML format.

On Fri, Feb 24, 2017 at 9:16 PM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us>
wrote:

> There is a little button near the bottom of the Gmail editing box that
> switches to plain text. We can immediately tell because of the
>
> [[alternative HTML version deleted]]
>
> line when we receive it, and sometimes it loses all of the line breaks or
> has extra asterisks mixed in. You can look in the archives or replies to
> see what we see.
> --
> Sent from my phone. Please excuse my brevity.
>
> On February 24, 2017 5:55:15 PM PST, C W <tmrsg11 at gmail.com> wrote:
> >I suppose for loop will suffice.
> >
> >I simply copy & paste the code from R editor. From my email, it looks
> >plain. Is there a way to tell?
> >
> >On Fri, Feb 24, 2017 at 8:50 PM, Jeff Newmiller
> ><jdnewmil at dcn.davis.ca.us>
> >wrote:
> >
> >> The apply function is one of many alienate ways to write a loop. It
> >is not
> >> appreciably more efficient in cpu time than a for loop.
> >>
> >> Your example creates the numbers in the loop... does your actual data
> >get
> >> created in a loop? If so then your original code should be perfectly
> >> serviceable. If not then there might be a better way to do this, but
> >you
> >> would have to expand your example to illustrate how the data comes to
> >you
> >> in order to suggest alternatives.
> >>
> >> Also post using plain text to prevent your code from being mangled on
> >its
> >> way to us.
> >> --
> >> Sent from my phone. Please excuse my brevity.
> >>
> >> On February 24, 2017 5:27:07 PM PST, C W <tmrsg11 at gmail.com> wrote:
> >> >In theory, I am generating from group 5 groups of random numbers,
> >each
> >> >group has 3 samples.
> >> >
> >> >Isn't apply() the replacement of loops?
> >> >
> >> >On Fri, Feb 24, 2017 at 8:23 PM, Jeff Newmiller
> >> ><jdnewmil at dcn.davis.ca.us>
> >> >wrote:
> >> >
> >> >> What is wrong with
> >> >>
> >> >> dat <- matrix(rnorm(15), nrow=5, ncol = 3)
> >> >>
> >> >> ?
> >> >>
> >> >> And what is this "no loop drama" you refer to? I use loops
> >frequently
> >> >to
> >> >> loop around large memory gobbling chunks of code.
> >> >>
> >> >> --
> >> >> Sent from my phone. Please excuse my brevity.
> >> >>
> >> >> On February 24, 2017 5:02:46 PM PST, C W <tmrsg11 at gmail.com>
> >wrote:
> >> >> >Dear R,
> >> >> >
> >> >> >I wanted to simulate a 5 by 3 matrix which fills up by either
> >rows
> >> >or
> >> >> >columns?
> >> >> >
> >> >> >I started with the following filling the matrix by rows,
> >> >> >
> >> >> >dat <- matrix(NA, nrow=5, ncol = 3)
> >> >> >
> >> >> >for(i in 1:5){
> >> >> >
> >> >> >    dat[i, ] <- rnorm(3)
> >> >> >
> >> >> >}
> >> >> >
> >> >> >But, R is known for no loop drama. Any suggestions?
> >> >> >
> >> >> >Thanks!
> >> >> >
> >> >> >       [[alternative HTML version deleted]]
> >> >> >
> >> >> >______________________________________________
> >> >> >R-help at 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.
> >> >>
> >>
>

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