R help - Jul 2007 - logical operators priority

Dear R-users,

I haven?t found rules for logical operators. I need to select data according
the following rule:
Condition A & (Condition B | Condition C) How should I write it?? Is
Condition A & Condition B | Condition C correct or will R execute (Condition
A & Condition B) | Condition C ?

Thanks for your help.

Delphine Fontaine






Delphine Fontaine
Statistician
Statistics Department - Genexion SA
------------------------------------------------------------
29, Quai du Mont-Blanc
Genva, CH-1201
Switzerland
------------------------------------------------------------
Office: +41 22 704 32 44
Fax:??? +41 22 704 32 42
Email: Delphine.Fontaine at genexion.com

Use parentheses if you want to be sure, otherwise the help file for &  
and | says:

See Syntax for the precedence of these operators: unlike many other  
languages (including S) the AND and OR operators do not have the same  
precedence (the AND operators are higher than the OR operators).

hth, Ingmar

On 17 Jul 2007, at 08:59, Delphine Fontaine wrote:
> Dear R-users,
>
> I haven’t found rules for logical operators. I need to select data  
> according
> the following rule:
> Condition A & (Condition B | Condition C) How should I write it ? Is
> Condition A & Condition B | Condition C correct or will R execute  
> (Condition
> A & Condition B) | Condition C ?
>
> Thanks for your help.
>
> Delphine Fontaine
>
>
>
>
>
>
> Delphine Fontaine
> Statistician
> Statistics Department - Genexion SA
> ------------------------------------------------------------
> 29, Quai du Mont-Blanc
> Genva, CH-1201
> Switzerland
> ------------------------------------------------------------
> Office: +41 22 704 32 44
> Fax:    +41 22 704 32 42
> Email: Delphine.Fontaine@genexion.com
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> 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.
Ingmar Visser
Department of Psychology, University of Amsterdam
Roetersstraat 15
1018 WB Amsterdam
The Netherlands
t: +31-20-5256735



	[[alternative HTML version deleted]]

?"&"

will show

See Syntax for the precedence of these operators: unlike many
other languages (including S) the AND and OR operators do not have
the same precedence (the AND operators are higher than the OR
operators).

Ted.


Delphine Fontaine wrote on 07/17/2007 04:59 PM:
> Dear R-users,
>
> I haven?t found rules for logical operators. I need to select data
according
> the following rule:
> Condition A & (Condition B | Condition C) How should I write it ? Is
> Condition A & Condition B | Condition C correct or will R execute
(Condition
> A & Condition B) | Condition C ?
>
> Thanks for your help.
>
> Delphine Fontaine
>
>
>
>
>
>
> Delphine Fontaine
> Statistician
> Statistics Department - Genexion SA
> ------------------------------------------------------------
> 29, Quai du Mont-Blanc
> Genva, CH-1201
> Switzerland
> ------------------------------------------------------------
> Office: +41 22 704 32 44
> Fax:    +41 22 704 32 42
> Email: Delphine.Fontaine at genexion.com
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> 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.
>   

-- 
 Dr E.A. Catchpole  
 Visiting Fellow
 Univ of New South Wales at ADFA, Canberra, Australia
    _	  and University of Kent, Canterbury, England
   'v'	  - www.pems.adfa.edu.au/~ecatchpole          
  /   \	  - fax: +61 2 6268 8786		   
   m m    - ph:  +61 2 6268 8895

On 17-Jul-07 06:59:11, Delphine Fontaine wrote:
> Dear R-users,
> 
> I haven't found rules for logical operators. I need to select data
> according the following rule:
> Condition A & (Condition B | Condition C)
> How should I write it_? Is Condition A & Condition B | Condition C
> correct or will R execute (Condition A & Condition B) | Condition C ?
> 
> Thanks for your help.
> 
> Delphine Fontaine
?Syntax will tell you about the precedence for operators.
In particular you will find:

       '!'                negation
       '&  &&'            and
       '| ||'             or

indicating that "!" takes precedence over "&" and
"&&", which take
precedence over "|" and "||". With equal precedence
evaluation is
from left to right.

This shows that if you write A & B | C then "A & B" will be
evaluated
first, so the expression is equivalent to (A & B) | C.

In any case, there is nothing whatever wrong with using "(... )"
for grouping. It is always accepted, it forces the precedence you want,
and furthermore (most important) you yourself can see exactly what
will happen and will be much less likely to make a mistake.

So write your condition in your code *explicitly* as

  ConditionA & (ConditionB | ConditionC)

You can see what's happening, and R will do exactly what you want.

Best wishes
Ted.

--------------------------------------------------------------------
E-Mail: (Ted Harding) <ted.harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 17-Jul-07                                       Time: 09:34:18
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