[R] how to break the loop using sapply?

[PO SU]

Is that mean while may be more effient than  for in R? as i know, while and for  are all just functions in R. 
Tks for your suggestion to not use apply that way, but i want to know, if possible, is there any way to break it ?
Actually, there is a additional question:
  x<- c(3,4,5,6,9)
 sapply(x ,function(i){
foo(i)  #do something to each value in x,how can i know the i's index in x?
)}
In my way , i always 
sapply(seq(x),function(i){
foo(x[i])
})
or 
Map( function(i,index){
foo(i)  # through index to know the i's index in x
},x ,seq(x)) 

How you solve the problem? I mean just use apply functions.



--

PO SU
mail: desolator88 at 163.com 
Majored in Statistics from SJTU




At 2014-10-10 13:58:29, "Jeff Newmiller" <jdnewmil at dcn.davis.CA.us> wrote:
>Don't use apply functions if you want to do what you describe. They don't work that way. Use a while control structure.
>
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>On October 9, 2014 10:24:49 PM PDT, PO SU <rhelpmaillist at 163.com> wrote:
>>
>>Dear expeRts,
>>   i  use sapply for loop, and i want to break it when i needed, how to
>>do that?  e.g.
>>
>>sapply( 1:10, function(i) {
>>if(i==5) break and jump out of the function sapply
>>} )
>>
>>I want to do it because i have to loop 1000000 times, but i don't know
>>when it will break, that means, it may need break at i=5 or at i=50000,
>>for the possible of the  last case, i don't use for loop, because it
>>slow(is it right?).
>>So,if you happen to know it ,may you help me?
>>
>>
>>--
>>
>>PO SU
>>mail: desolator88 at 163.com 
>>Majored in Statistics from SJTU
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>