Re: [R] is there any method to defer the execution of code in r?

[Rui Barradas]

Hello,

I don't understand.
It *is* the same question. Same code, same words. And same 'AKSHAY  M 
KULKARNI' (the OP here) and 'AKshayKulkarni' (SO).

Exactly the same.

Rui Barradas

On 5/13/2018 2:07 PM, Jeff Newmiller wrote:
I am puzzled by the use of the term "cross-posted" here... I don't see the OP 
or their question or any similar words from the question involved the the given link, 
though that link seems worth bringing it to the OP's attention.

But the function given in the question seems to have other problems:

A) The download.file function call puts its result in a different place than 
the read.csv reads data from. Unless the OP is manually moving files around 
with the  file browser in the background I don't see how this would ever work.

B) The file paths refer to C:/Users/user ... it would be highly unusual for 
there to be such a directory on any machine, so I am wondering how close any of 
this code is to what the OP actually did.

C) Reading the help page for download.file, it appears to behave like most 
functions in R... it does not return until the operation is complete. That is, 
the premise of the question seems flawed, and a truly reproducible example 
would be needed to convince me to go down the delay rabbit hole. The OP has 
been around this list long enough to know where to go to find out how to make a 
reproducible example.


On May 13, 2018 1:16:47 AM PDT, Rui Barradas <ruipbarra...@sapo.pt> wrote:
Hello,

This is cross posted from StackOverflow:

https://stackoverflow.com/questions/50314015/is-there-any-method-to-defer-the-execution-of-code-in-r

Cross posting is discouraged in r-help.

Rui Barradas

On 5/13/2018 8:59 AM, akshay kulkarni wrote:
dear members,

I have created the following function to read a csv file from a given
URL:

      function(){
                              s <- 1;

                              #first get the bhav copy
                              today <- c();ty <- c();tm <- c();tmu <-
c();td <- c();

                             # get the URL first
                              today <- Sys.Date()
                              ty <- format(today, format = "%Y")
                              tm <- format(today, format = "%b")
                              tmu <- toupper(tm)
                              td <- format(today, format = "%d")

             dynamic.URL <-
paste("https://www.nseindia.com/content/historical/EQUITIES/",ty,"/",tmu,"/cm",td,tmu,ty,"bhav.csv.zip";,
sep = "")
             file.string <-
paste("C:/Users/user/AppData/Local/Temp/cm",td,tmu,ty,"bhav.csv")

                              download.file(dynamic.URL,
"C:/Users/user/Desktop/bhav.csv.zip")
                              bhav.copy <- read.csv(file.string)
                              return(bhav.copy)
      }

If I run the function, immediately it says that "file.string not
found". But when I run it after some time(a few seconds), it executes
normally. I think when `download.file` ecexecutes, it transfers control
to `read.csv, `and it tries to load the file which is not yet properly
saved. when I run it after some time, it tries to overwrite the
existing file, which it cannot, and the `read.csv`properly loads the
saved file.`

I want the function to execute the first time I run it. Is there any
way or a function to defer the action of `read.csv`until the file is
properly saved? Something like this:

      download.file(dynamic.URL, "C:/Users/user/Desktop/bhav.csv.zip")
                                  wait......
                                  bhav.copy <- read.csv(file.string)

Ignore the fact that the destfile in download.file is different from
file.string; it is due to function of my system (windows 7).

Very many thanks for your time and effort...

AKSHAY  M KULKARNI


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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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