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

Rui Barradas ru|pb@rr@d@@ @end|ng |rom @@po@pt
Sun Dec 11 18:28:50 CET 2022

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,
> 	[[alternative HTML version deleted]]
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> and provide commented, minimal, self-contained, reproducible code.

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

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