[R] R Programming help needed - Returning dataframes + 2 Variables dynamically

Mathew Guilfoyle mrguilfoyle at gmail.com
Fri Jul 28 11:08:42 CEST 2017


The returned values are in the list you assign to test_data, the original x and y are not modified, i.e the returned value for x will be test_data[[1]] and for y will be test_data[[2]].  Using the same variable names in the function and test is perhaps what is leading to confusion.

> On 28 Jul 2017, at 09:13, Vijaya Kumar Regati <VijayaKumar.Regati at m3bi.com> wrote:
> 
> Hi,
> 
> 
> That was very useful information. Thanks.
> 
> But still I am not able to get the desired output with updated code.
> 
> Kindly help if you have any further thoughts ...
> 
> Updated code :
> x <- 0
> y <- 0
> 
> Logic_fn <- function(x,y){
> 
> print("Passed Values")
> print(x)
> print(y)
> x <- x + 1
> y <- y + 1
> 
> print("After addition :")
> print(x)
> print(y)
> 
> test_data <- rbind(x,y)
> test_data <- data.frame(test_data)
> return(list(x,y,test_data))
> }
> 
> for ( i in 1:1 ) {
> test_data <- Logic_fn(x,y)
> print("Returned Values :")
> print(x)
> print(y)
> }
> 
> 
> Wrong output :
> [1] "Passed Values"
> [1] 0
> [1] 0
> [1] "After addition :"
> [1] 1
> [1] 1
> [1] "Returned Values :"
> [1] 0
> [1] 0
> 
> 
> With Regards,
> Vijaya Kumar Regati
> Technical Lead, M3bi India Private Ltd
> Work: 040-67064732
> 
> ________________________________
> From: Koustav Pal <koustavpal.devel at gmail.com>
> Sent: Friday, July 28, 2017 12:25:54 PM
> To: Vijaya Kumar Regati
> Cc: vijaykr.sas at gmail.com; r-help at R-project.org
> Subject: Re: [R] R Programming help needed - Returning dataframes + 2 Variables dynamically
> 
> c() is used for constructing vectors. Or in other words using the method c(x,y) provides a vector of length 2 (hopefully). Therefore, you are pushing a single vector to your function and not two arguments as you want.
> 
> It should be Logic_fn(x,y) not Logic_fn(c(x,y)).
> 
> Furthermore, i would recommend reading up on how function constructs work. Two return statements within a function are redundant because the function will exit after the first return statement, and anything else just creates more ambiguity. If you want to return the x y variables as well, you should use a list like so, list(test_data, x, y) and then retrieve information from the list like this Boo[[1]].....
> 
> Finally i would also like to point out that you should note R's behaviour unless explicitly stated while calling the function is to assign the first argument to the first declared variable and the second to the second. So, if you called Logic_fn(y,x), then y will be assigned to x and x to y. So to avoid such a scenario you can mention it explicitly as Logic_fn(y=y,x=x).
> 
> 
> On Jul 28, 2017 8:39 AM, "Vijaya Kumar Regati" <VijayaKumar.Regati at m3bi.com<mailto:VijayaKumar.Regati at m3bi.com>> wrote:
> Hi,
> 
> 
> Can someone please help me on below issue I am facing :
> 
> 
> I am trying to play with returning a dataframe+2 variables using a fn.
> But facing an issue :
> 
> Error in Logic_fn(c(x, y)) : argument "y" is missing, with no default
> 
> This is the code I am using :
> 
> 
> x <- 0
> y <- 0
> 
> Logic_fn <- function(x,y){
> x <- x + 1
> y < y + 1
> test_data <- rbind(x,y)
> test_data <- data.frame(test_data)
> return(test_data)
> return(c(x,y))
> }
> 
> for ( i in 1:1) {
>  test_data <- Logic_fn(c(x,y))
> test_data[1]
> test_data[2]
> test_data
> 
> }
> 
> With Regards,
> Vijaya Kumar Regati
> 
> 
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