thr3ads.net - R help - [R] Subset with missing argument within a function [Feb 2016]

If this information is useful, please help other people find it:
Share via:

Stefano de Pretis

2016-Feb-04 10:00 UTC

[R] Subset with missing argument within a function

Hi all,

I'm guessing what's the rationale behind this:
> subsettingFun <- function(vec, ix) vec[ix]
> subsettingFun(letters, c(1,2,5))
[1] "a" "b" "e"> subsettingFun(letters) [1] "a" "b" "c" "d" "e"
"f" "g" "h" "i" "j"
"k" "l" "m" "n" "o"
"p" "q"
"r" "s"
[20] "t" "u" "v" "w" "x"
"y" "z"

If the argument "ix" is missing, I'm expecting an error not to
return the
variable "vec" as it is.

I think this is VERY dangerous and does not help the development of
reliable code and the debugging.

Cheers,

Stefano

*Center for Genomic Science of IIT at SEMM*

Stefano de Pretis, PhD

*Postdoctoral fellow *

	[[alternative HTML version deleted]]

PIKAL Petr

2016-Feb-04 14:39 UTC

head link

[R] Subset with missing argument within a function

Hi

Help page for ?"[" says

An empty index selects all values: this is most often used to replace all the
entries but keep the attributes.

and actually you function construction works with empty index
> x<-c(1,2,5)
> letters[x]
[1] "a" "b" "e"> letters[] [1] "a" "b" "c" "d" "e"
"f" "g" "h" "i" "j"
"k" "l" "m" "n" "o"
"p" "q" "r" "s"
[20] "t" "u" "v" "w" "x"
"y" "z"

It is sometimes useful not "expect" the program behavior but
"inspect" why it behaves differently.

If you want your function to throw error when some arguments are missing you
need to do the check yourself and not rely on programming language.

And BTW I did not know an answer before I inspected docs.

Cheers
Petr

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Stefano
> de Pretis
> Sent: Thursday, February 04, 2016 11:00 AM
> To: r-help at r-project.org
> Subject: [R] Subset with missing argument within a function
>
> Hi all,
>
> I'm guessing what's the rationale behind this:
>
> > subsettingFun <- function(vec, ix) vec[ix]
> > subsettingFun(letters, c(1,2,5))
> [1] "a" "b" "e"
> > subsettingFun(letters)
>  [1] "a" "b" "c" "d" "e"
"f" "g" "h" "i" "j"
"k" "l" "m" "n" "o"
"p"
> "q"
> "r" "s"
> [20] "t" "u" "v" "w" "x"
"y" "z"
>
> If the argument "ix" is missing, I'm expecting an error not
to return
> the
> variable "vec" as it is.
>
> I think this is VERY dangerous and does not help the development of
> reliable code and the debugging.
>
> Cheers,
>
> Stefano
>
> *Center for Genomic Science of IIT at SEMM*
>
> Stefano de Pretis, PhD
>
> *Postdoctoral fellow *
>
>       [[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.
________________________________
Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou d?v?rn? a jsou ur?eny
pouze jeho adres?t?m.
Jestli?e jste obdr?el(a) tento e-mail omylem, informujte laskav? neprodlen? jeho
odes?latele. Obsah tohoto emailu i s p??lohami a jeho kopie vyma?te ze sv?ho
syst?mu.
Nejste-li zam??len?m adres?tem tohoto emailu, nejste opr?vn?ni tento email
jakkoliv u??vat, roz?i?ovat, kop?rovat ?i zve?ej?ovat.
Odes?latel e-mailu neodpov?d? za eventu?ln? ?kodu zp?sobenou modifikacemi ?i
zpo?d?n?m p?enosu e-mailu.

V p??pad?, ?e je tento e-mail sou??st? obchodn?ho jedn?n?:
- vyhrazuje si odes?latel pr?vo ukon?it kdykoliv jedn?n? o uzav?en? smlouvy, a
to z jak?hokoliv d?vodu i bez uveden? d?vodu.
- a obsahuje-li nab?dku, je adres?t opr?vn?n nab?dku bezodkladn? p?ijmout;
Odes?latel tohoto e-mailu (nab?dky) vylu?uje p?ijet? nab?dky ze strany p??jemce
s dodatkem ?i odchylkou.
- trv? odes?latel na tom, ?e p??slu?n? smlouva je uzav?ena teprve v?slovn?m
dosa?en?m shody na v?ech jej?ch n?le?itostech.
- odes?latel tohoto emailu informuje, ?e nen? opr?vn?n uzav?rat za spole?nost
??dn? smlouvy s v?jimkou p??pad?, kdy k tomu byl p?semn? zmocn?n nebo p?semn?
pov??en a takov? pov??en? nebo pln? moc byly adres?tovi tohoto emailu p??padn?
osob?, kterou adres?t zastupuje, p?edlo?eny nebo jejich existence je adres?tovi
?i osob? j?m zastoupen? zn?m?.

This e-mail and any documents attached to it may be confidential and are
intended only for its intended recipients.
If you received this e-mail by mistake, please immediately inform its sender.
Delete the contents of this e-mail with all attachments and its copies from your
system.
If you are not the intended recipient of this e-mail, you are not authorized to
use, disseminate, copy or disclose this e-mail in any manner.
The sender of this e-mail shall not be liable for any possible damage caused by
modifications of the e-mail or by delay with transfer of the email.

In case that this e-mail forms part of business dealings:
- the sender reserves the right to end negotiations about entering into a
contract in any time, for any reason, and without stating any reasoning.
- if the e-mail contains an offer, the recipient is entitled to immediately
accept such offer; The sender of this e-mail (offer) excludes any acceptance of
the offer on the part of the recipient containing any amendment or variation.
- the sender insists on that the respective contract is concluded only upon an
express mutual agreement on all its aspects.
- the sender of this e-mail informs that he/she is not authorized to enter into
any contracts on behalf of the company except for cases in which he/she is
expressly authorized to do so in writing, and such authorization or power of
attorney is submitted to the recipient or the person represented by the
recipient, or the existence of such authorization is known to the recipient of
the person represented by the recipient.

Stefano de Pretis

2016-Feb-04 15:47 UTC

head link

[R] Subset with missing argument within a function

Hi Petr,

Thank you for your answer.

I'm not sure how the empty index reflects what I'm showing in my
example.
If my function was

emptySubset <- function(vec) vec[]

I would then agree that this was the case. But I think it's different:
I'm
specifically telling my function that it should have two arguments
("vec"
and "ix")

subsettingFun <- function(vec, ix) vec[ix]

and I guess why, within the function, it does not happen what happens on
the command line:
> ix
Error: object 'ix' not found> letters[ix]Error: object 'ix' not found

My "expectation" came from a matter of coherence, but probably I'm
still
missing something.

Regards,

Stefano



2016-02-04 15:39 GMT+01:00 PIKAL Petr <petr.pikal at precheza.cz>:
> Hi
>
> Help page for ?"[" says
>
> An empty index selects all values: this is most often used to replace all
> the entries but keep the attributes.
>
> and actually you function construction works with empty index
>
> > x<-c(1,2,5)
> > letters[x]
> [1] "a" "b" "e"
> > letters[]
>  [1] "a" "b" "c" "d" "e"
"f" "g" "h" "i" "j"
"k" "l" "m" "n" "o"
"p" "q"
> "r" "s"
> [20] "t" "u" "v" "w" "x"
"y" "z"
>
> It is sometimes useful not "expect" the program behavior but
"inspect" why
> it behaves differently.
>
> If you want your function to throw error when some arguments are missing
> you need to do the check yourself and not rely on programming language.
>
> And BTW I did not know an answer before I inspected docs.
>
> Cheers
> Petr
>
>
> > -----Original Message-----
> > From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
Stefano
> > de Pretis
> > Sent: Thursday, February 04, 2016 11:00 AM
> > To: r-help at r-project.org
> > Subject: [R] Subset with missing argument within a function
> >
> > Hi all,
> >
> > I'm guessing what's the rationale behind this:
> >
> > > subsettingFun <- function(vec, ix) vec[ix]
> > > subsettingFun(letters, c(1,2,5))
> > [1] "a" "b" "e"
> > > subsettingFun(letters)
> >  [1] "a" "b" "c" "d"
"e" "f" "g" "h" "i"
"j" "k" "l" "m" "n"
"o" "p"
> > "q"
> > "r" "s"
> > [20] "t" "u" "v" "w"
"x" "y" "z"
> >
> > If the argument "ix" is missing, I'm expecting an error
not to return
> > the
> > variable "vec" as it is.
> >
> > I think this is VERY dangerous and does not help the development of
> > reliable code and the debugging.
> >
> > Cheers,
> >
> > Stefano
> >
> > *Center for Genomic Science of IIT at SEMM*
> >
> > Stefano de Pretis, PhD
> >
> > *Postdoctoral fellow *
> >
> >       [[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.
>
> ________________________________
> Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou d?v?rn? a jsou
> ur?eny pouze jeho adres?t?m.
> Jestli?e jste obdr?el(a) tento e-mail omylem, informujte laskav?
> neprodlen? jeho odes?latele. Obsah tohoto emailu i s p??lohami a jeho kopie
> vyma?te ze sv?ho syst?mu.
> Nejste-li zam??len?m adres?tem tohoto emailu, nejste opr?vn?ni tento email
> jakkoliv u??vat, roz?i?ovat, kop?rovat ?i zve?ej?ovat.
> Odes?latel e-mailu neodpov?d? za eventu?ln? ?kodu zp?sobenou modifikacemi
> ?i zpo?d?n?m p?enosu e-mailu.
>
> V p??pad?, ?e je tento e-mail sou??st? obchodn?ho jedn?n?:
> - vyhrazuje si odes?latel pr?vo ukon?it kdykoliv jedn?n? o uzav?en?
> smlouvy, a to z jak?hokoliv d?vodu i bez uveden? d?vodu.
> - a obsahuje-li nab?dku, je adres?t opr?vn?n nab?dku bezodkladn? p?ijmout;
> Odes?latel tohoto e-mailu (nab?dky) vylu?uje p?ijet? nab?dky ze strany
> p??jemce s dodatkem ?i odchylkou.
> - trv? odes?latel na tom, ?e p??slu?n? smlouva je uzav?ena teprve
> v?slovn?m dosa?en?m shody na v?ech jej?ch n?le?itostech.
> - odes?latel tohoto emailu informuje, ?e nen? opr?vn?n uzav?rat za
> spole?nost ??dn? smlouvy s v?jimkou p??pad?, kdy k tomu byl p?semn? zmocn?n
> nebo p?semn? pov??en a takov? pov??en? nebo pln? moc byly adres?tovi tohoto
> emailu p??padn? osob?, kterou adres?t zastupuje, p?edlo?eny nebo jejich
> existence je adres?tovi ?i osob? j?m zastoupen? zn?m?.
>
> This e-mail and any documents attached to it may be confidential and are
> intended only for its intended recipients.
> If you received this e-mail by mistake, please immediately inform its
> sender. Delete the contents of this e-mail with all attachments and its
> copies from your system.
> If you are not the intended recipient of this e-mail, you are not
> authorized to use, disseminate, copy or disclose this e-mail in any manner.
> The sender of this e-mail shall not be liable for any possible damage
> caused by modifications of the e-mail or by delay with transfer of the
> email.
>
> In case that this e-mail forms part of business dealings:
> - the sender reserves the right to end negotiations about entering into a
> contract in any time, for any reason, and without stating any reasoning.
> - if the e-mail contains an offer, the recipient is entitled to
> immediately accept such offer; The sender of this e-mail (offer) excludes
> any acceptance of the offer on the part of the recipient containing any
> amendment or variation.
> - the sender insists on that the respective contract is concluded only
> upon an express mutual agreement on all its aspects.
> - the sender of this e-mail informs that he/she is not authorized to enter
> into any contracts on behalf of the company except for cases in which
> he/she is expressly authorized to do so in writing, and such authorization
> or power of attorney is submitted to the recipient or the person
> represented by the recipient, or the existence of such authorization is
> known to the recipient of the person represented by the recipient.
>
	[[alternative HTML version deleted]]

R help - Feb 2016 - Subset with missing argument within a function

[R] Subset with missing argument within a function

[R] Subset with missing argument within a function

[R] Subset with missing argument within a function