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David Carlson

2021-Jun-06 19:21 UTC

[R] Beginner problem - using mod function to print odd numbers

There is really no need for a loop:

num <- 1:100
num[ifelse(num %% 2 == 1, TRUE, FALSE)]

 [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
[26] 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99

David L Carlson


On Sat, Jun 5, 2021 at 2:05 PM William Michels via R-help
<r-help at r-project.org> wrote:>
> > i <- 1L; span <- 1:100; result <- NA;
> > for (i in span){
> + ifelse(i %% 2 != 0, result[i] <- TRUE, result[i] <- FALSE)
> + }
> > span[result]
>  [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43
> 45 47 49 51 53 55 57
> [30] 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99
> >
>
> HTH, Bill.
>
> W. Michels, Ph.D.
>
>
> On Sat, Jun 5, 2021 at 12:55 AM Stefan Evert <stefanML at
collocations.de> wrote:
> >
> > >
> > > I don't understand. --
> > >
> > > 7%%2=1
> > > 9%%2=1
> > > 11%%2=1
> > >
> > > What aren't these numbers printing ?
> > >
> > > num<-0
> > > for (i in 1:100){
> > >  num<-num+i
> > > if (num%%2 != 0)
> > >  print(num)
> > > }
> >
> > Your code tests the numbers
> >
> >         1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, ?
> >
> > and correctly prints the odd ones among them.
> >
> > But I suppose that's not what you wanted to do?
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >
https://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-help__;!!KwNVnqRv!Qe700OYnXI-Qe4XYE55MkVqMX3g4Ic4YFx87U-moxnT0xKw7m-rbNqU-EZd5ixk$
> > PLEASE do read the posting guide
https://urldefense.com/v3/__http://www.R-project.org/posting-guide.html__;!!KwNVnqRv!Qe700OYnXI-Qe4XYE55MkVqMX3g4Ic4YFx87U-moxnT0xKw7m-rbNqU-fWVQ0xI$
> > and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>
https://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-help__;!!KwNVnqRv!Qe700OYnXI-Qe4XYE55MkVqMX3g4Ic4YFx87U-moxnT0xKw7m-rbNqU-EZd5ixk$
> PLEASE do read the posting guide
https://urldefense.com/v3/__http://www.R-project.org/posting-guide.html__;!!KwNVnqRv!Qe700OYnXI-Qe4XYE55MkVqMX3g4Ic4YFx87U-moxnT0xKw7m-rbNqU-fWVQ0xI$
> and provide commented, minimal, self-contained, reproducible code.

David Carlson

2021-Jun-06 20:09 UTC

head link

[R] Beginner problem - using mod function to print odd numbers

If the loop is necessary:

num <- vector()
for (i in 1:100) {
    if(i %% 2 != 0) num <- c(num, i)
}
num

Or modify your code to this to get each odd number printed on a separate row:

for (i in 1:100) {
    if(i %% 2 != 0) print(i)
}

David L Carlson

On Sun, Jun 6, 2021 at 3:21 PM David Carlson <dcarlson at tamu.edu>
wrote:>
> There is really no need for a loop:
>
> num <- 1:100
> num[ifelse(num %% 2 == 1, TRUE, FALSE)]
>
>  [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45
47 49
> [26] 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95
97 99
>
> David L Carlson
>
>
> On Sat, Jun 5, 2021 at 2:05 PM William Michels via R-help
> <r-help at r-project.org> wrote:
> >
> > > i <- 1L; span <- 1:100; result <- NA;
> > > for (i in span){
> > + ifelse(i %% 2 != 0, result[i] <- TRUE, result[i] <- FALSE)
> > + }
> > > span[result]
> >  [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43
> > 45 47 49 51 53 55 57
> > [30] 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99
> > >
> >
> > HTH, Bill.
> >
> > W. Michels, Ph.D.
> >
> >
> > On Sat, Jun 5, 2021 at 12:55 AM Stefan Evert <stefanML at
collocations.de> wrote:
> > >
> > > >
> > > > I don't understand. --
> > > >
> > > > 7%%2=1
> > > > 9%%2=1
> > > > 11%%2=1
> > > >
> > > > What aren't these numbers printing ?
> > > >
> > > > num<-0
> > > > for (i in 1:100){
> > > >  num<-num+i
> > > > if (num%%2 != 0)
> > > >  print(num)
> > > > }
> > >
> > > Your code tests the numbers
> > >
> > >         1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, ?
> > >
> > > and correctly prints the odd ones among them.
> > >
> > > But I suppose that's not what you wanted to do?
> > >
> > > ______________________________________________
> > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
see
> > >
https://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-help__;!!KwNVnqRv!Qe700OYnXI-Qe4XYE55MkVqMX3g4Ic4YFx87U-moxnT0xKw7m-rbNqU-EZd5ixk$
> > > PLEASE do read the posting guide
https://urldefense.com/v3/__http://www.R-project.org/posting-guide.html__;!!KwNVnqRv!Qe700OYnXI-Qe4XYE55MkVqMX3g4Ic4YFx87U-moxnT0xKw7m-rbNqU-fWVQ0xI$
> > > and provide commented, minimal, self-contained, reproducible
code.
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >
https://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-help__;!!KwNVnqRv!Qe700OYnXI-Qe4XYE55MkVqMX3g4Ic4YFx87U-moxnT0xKw7m-rbNqU-EZd5ixk$
> > PLEASE do read the posting guide
https://urldefense.com/v3/__http://www.R-project.org/posting-guide.html__;!!KwNVnqRv!Qe700OYnXI-Qe4XYE55MkVqMX3g4Ic4YFx87U-moxnT0xKw7m-rbNqU-fWVQ0xI$
> > and provide commented, minimal, self-contained, reproducible code.

Martin Maechler

2021-Jun-09 09:55 UTC

head link

[R] Beginner problem - using mod function to print odd numbers

>>>>> David Carlson    on Sun, 6 Jun 2021 15:21:34 -0400 writes:
> There is really no need for a loop:
> num <- 1:100
> num[ifelse(num %% 2 == 1, TRUE, FALSE)]
> [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47
49
> [26] 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95
97 99
Well, and the above "works" but is really another proof of my
year-long claim that people use  ifelse(.)  *MUCH MUCH* too often,
and should really learn to use alternatives, in this case,
"R 101" (*long* before fooverse):

Use

    num[num %% 2 == 1]

instead of much slower and ...@#^$

    num[ifelse(num %% 2 == 1, TRUE, FALSE)]

Martin Maechler
ETH Zurich 
> On Sat, Jun 5, 2021 at 2:05 PM William Michels via R-help
> <r-help at r-project.org> wrote:    >> 
    >> > i <- 1L; span <- 1:100; result <- NA;
    >> > for (i in span){
    >> + ifelse(i %% 2 != 0, result[i] <- TRUE, result[i] <- FALSE)
    >> + }
    >> > span[result]
    >> [1]  1  3  5  7  9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41
43

 [............]

R help - Jun 2021 - Beginner problem - using mod function to print odd numbers

[R] Beginner problem - using mod function to print odd numbers

[R] Beginner problem - using mod function to print odd numbers

[R] Beginner problem - using mod function to print odd numbers