Petr's suggestion to replace NULL by 0. I just wanted
to indicate that it could produce unwanted results in several cases.
Philippe
>>
>> Best,
>>
>> Philippe
>>
>>
>> > Regards
>> > Petr
>> >
>> >
>> >>
roject.org] On Behalf Of PO SU
>> Sent: Thursday, September 11, 2014 3:54 AM
>> To: Duncan Murdoch
>> Cc: R. Help
>> Subject: Re: [R] some question about vector[-NULL]
>>
>>
>> Tks, i think using logical index is a way, but to do that, i have to
>> keep a v
org] On Behalf Of PO SU
>> Sent: Thursday, September 11, 2014 3:54 AM
>> To: Duncan Murdoch
>> Cc: R. Help
>> Subject: Re: [R] some question about vector[-NULL]
>>
>>
>> Tks, i think using logical index is a way, but to do that, i have to
>> keep a ve
On 11/09/2014, 6:04 AM, PO SU wrote:
>
>
> Actually, i thought the way:
> a<-1:3
> b<-NULL or 2
> a[-b] will not work if b is NULL
>
> A<-c(a,1)
If a is a long vector, that is a very expensive operation, at least as
expensive as constructing a logical vector of the same length as a.
> B<-c(b
Actually, i thought the way:
a<-1:3
b<-NULL or 2
a[-b] will not work if b is NULL
A<-c(a,1)
B<-c(b,length(A))
A[-B] will get the same result as if b is NULL get a, if b is 2 get a[-2]
I think it works well in considering memory use or efficiency or code tidy.
--
PO SU
mail: desolato...@
Orignally i don't want to do the if ( length) check because i know that in a
1 loops, after may be 10 or 20 or 100 loops , "i" will not be empty.
so i mean , in the left loops, i would always check something not needed to
check which i would not like to do.
--
PO SU
mail: desolato...@1
On 10/09/2014, 9:53 PM, PO SU wrote:
>
> Tks, i think using logical index is a way, but to do that, i have to keep a
> vector as long as the original vector. that's, to exclude position 1 and 3
> from
> a<-1:5
> I have to let b<-c(F,T,F,T,T) and exec a[b], not a[-c(1,3)]. which c(1,3) is
> muc
behaviour
would change almost any R code I am afraid that you need to reprogram it
yourself.
Regards
Petr
> -Original Message-
> From: PO SU [mailto:rhelpmaill...@163.com]
> Sent: Thursday, September 11, 2014 9:27 AM
> To: PIKAL Petr
> Cc: R. Help
> Subject: Re
t;
>
>> -Original Message-
>> From: r-help-boun...@r-project.org [mailto:r-help-bounces@r-
>> project.org] On Behalf Of PO SU
>> Sent: Thursday, September 11, 2014 3:54 AM
>> To: Duncan Murdoch
>> Cc: R. Help
>> Subject: Re: [R] some question
roject.org] On Behalf Of PO SU
> Sent: Thursday, September 11, 2014 3:54 AM
> To: Duncan Murdoch
> Cc: R. Help
> Subject: Re: [R] some question about vector[-NULL]
>
>
> Tks, i think using logical index is a way, but to do that, i have to
> keep a vector as long as the ori
Tks, i think using logical index is a way, but to do that, i have to keep a
vector as long as the original vector. that's, to exclude position 1 and 3 from
a<-1:5
I have to let b<-c(F,T,F,T,T) and exec a[b], not a[-c(1,3)]. which c(1,3) is
much shorter than b if a is a long vector. that's, b wo
On 10/09/2014 12:20 PM, William Dunlap wrote:
Can you make your example a bit more concrete? E.g., is your 'index
vector' A an integer vector? If so, integer(0), an integer vector
with no elements, would be a more reasonable return value than NULL,
an object of class NULL with length 0, for the
Can you make your example a bit more concrete? E.g., is your 'index
vector' A an integer vector? If so, integer(0), an integer vector
with no elements, would be a more reasonable return value than NULL,
an object of class NULL with length 0, for the 'not found' case and
you could check for that c
May be i could add a extra elment to B,that's:
F<-function( C ) {
C<-C[-A]
some processing...
res<-NULL or some new index not included in A
return(res)
}
so in a loop,
C<-c(B,1)
tmpindex<-length(C)
A<-tmpindex
for( i in 1:10) {
D<-F(C)
A<-c(A,D)
}
--
PO SU
mail: desolato...@163.com
M
Tks for your
a <- list(ress = 1, res = NULL)
And in my second question, let me explain it :
Actually i have two vectors in global enviroment, called A and B .A is
initialized to NULL which used to record some index in B.
Then i would run a function F, and each time, i would get a index value o
On 10/09/2014, 3:21 AM, PO SU wrote:
>
> Dear expeRts,
> I have some programming questions about NULL in R.There are listed as
> follows:
> 1. I find i can't let a list have a element NULL:
> a<-list()
> a$ress<-1
> a$res<-NULL
> a
> str(a)
You can do it using
a <- list(ress = 1, res = NU
[unlist(lapply(a, function(x) !is.null(x)))]
Regards
Petr
> -Original Message-
> From: r-help-boun...@r-project.org [mailto:r-help-bounces@r-
> project.org] On Behalf Of PO SU
> Sent: Wednesday, September 10, 2014 9:21 AM
> To: R. Help
> Subject: [R] some question about
Dear expeRts,
I have some programming questions about NULL in R.There are listed as
follows:
1. I find i can't let a list have a element NULL:
a<-list()
a$ress<-1
a$res<-NULL
a
str(a)
How can i know i have a named element but it is NULL, not just get
a$,a$,a$ there all get NUL
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