[R] remembering the state of an action in R....

[Rui Barradas]

Às 17:28 de 11/12/2022, Rui Barradas escreveu:
> Às 17:11 de 11/12/2022, akshay kulkarni escreveu:
>> Dear members,
>>                              I am a stock trader and using R for my 
>> research. I am monitoring stock prices in real time. I have the 
>> following code:
>>
>>> if (sock price q, breaches a certain value Q) { expr1; expr2; expr3}
>>
>> THe point is, expr1,expr2,expr3 should execute only once, i.e when q 
>> breaches Q. I thought of something like this:
>>
>>> if( q >= Q ) { expr1; expr2; expr3;}
>>
>> But expressions keep repeating as long as q >= Q, NOT when q breaches 
>> Q for the first time. I did some research on myself and came up with 
>> this:
>>
>>> f <- function() {expr1; expr2; expr3; j <<- j + 1}
>>> j <- 1; counter[[j]] <- 1;
>>> if ((q >= Q)  && length(counter) == 1) {f}
>>
>> I just want your help to know whether it is logically right or not. 
>> ARe not there any other possibility other than using the 
>> superassignment operator?
>>
>> Also, any way how to remember when the real time price q, breaches a 
>> value Q, for the first time ( the price may come back to Q again 
>> afterwards) ?
>>
>> THanking you,
>> Yours sincerely,
>> AKSHAY M KULKARNI
>>
>>     [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help using 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.
> Hello,
> 
> Use environments. You will assign to a variable living in a special 
> place, protected from the rest of the code, that you can access any time 
> you want.
> Something like the following.
> 
> 
> 
> f <- function(envir) {expr1; expr2; expr3; envir$j <- envir$j + 1L}
> 
> e <- new.env()
> e$j <- 1L
> # do you need counter for something else?
> # if not delete these two lines
> counter <- list()
> counter[[e$j]] <- 1L
> # this seems to be all you need, not counter
> if ((q >= Q)  && e$j == 1L) {f(e)}
> 
> 
> 
> Hope this helps,
> 
> Rui Barradas
> 
> ______________________________________________
> R-help using 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.
Hello,

Or with a counter.


f <- function(envir) {
   envir$counter <- envir$counter + 1L
   x <- pi
   x
}

q <- 10
Q <- 5
e <- new.env()
e$counter <- 0L
#
if ((q >= Q)  && e$counter == 0L) {
   print(f(e))
}
#> [1] 3.141593

if ((q >= Q)  && e$counter == 0L) {
   print(f(e))
} else message("it worked!")
#> it worked!


Hope this helps,

Rui Barradas