[R] Creating Functions in R

[jim holtman]

Modified your function and also you don't need a function to do this:

sub <- structure(list(week = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,
29, 30), value = c(9.45, 7.99, 9.29, 11.66, 12.16, 10.18, 8.04,
11.46, 9.2, 10.34, 9.03, 11.47, 10.51, 9.4, 10.08, 9.37, 10.62,
10.31, 10, 13, 10.9, 9.33, 12.29, 11.5, 10.6, 11.08, 10.38, 11.62,
11.31, 10.52)), .Names = c("week", "value"), row.names = c(NA,
-30L), class = "data.frame")

vmask <- function(data,target){
    data$deviation <- data$value - target
    data  # return value
}


newSub <- vmask(sub,10)  # need to assign return value
View(newSub)

# do the same thing without a function
sub$deviation <- sub$value - 10
View(sub)



Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.


On Thu, Jul 24, 2014 at 10:17 AM, David L Carlson <dcarlson at tamu.edu> wrote:
> Before you start writing functions, you should learn the basics of R by reading "An Introduction to R" (http://cran.r-project.org/doc/manuals/r-release/R-intro.pdf). Pages 7 and 8 cover what you are asking. There is no need for a for() loop at all and your function is simply overwriting the value of "deviation" so you only get the last value recycled (page 20, "The recycling rule").
>
> -------------------------------------
> David L Carlson
> Department of Anthropology
> Texas A&M University
> College Station, TX 77840-4352
>
>
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Pavneet Arora
> Sent: Thursday, July 24, 2014 8:36 AM
> To: r-help at r-project.org
> Subject: [R] Creating Functions in R
>
> Hello Guys
> I am new at writing Functions in R, and as a result am struggling with it.
> I am trying to use Google & other resources, but it's hard to find
> solutions when you don't know what to look for.
>
> I have the following small dataset
>> dput(sub)
> structure(list(week = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
> 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,
> 29, 30), value = c(9.45, 7.99, 9.29, 11.66, 12.16, 10.18, 8.04,
> 11.46, 9.2, 10.34, 9.03, 11.47, 10.51, 9.4, 10.08, 9.37, 10.62,
> 10.31, 10, 13, 10.9, 9.33, 12.29, 11.5, 10.6, 11.08, 10.38, 11.62,
> 11.31, 10.52)), .Names = c("week", "value"), row.names = c(NA,
> -30L), class = "data.frame")
>
> I want to take each of the value and subtract from a target {in this case
> its 10}. This is what I have written in my function so far:
> vmask <- function(data,target){
> for(k in 1:length(data))
> deviation <- data[k]- target
> dev <- return(data.frame(cbind(data,deviation)))
> return(dev)
> }
> vmask(sub,10)
> View(dev)
>
> But when I run this I get the results as expected. But I expected the new
> coloumn to be called "deviation", whereas R just calls in "value.1". How
> can I fix this?
> Also I was hoping to see this new dataset with columns "week", "value",
> and now "deviation" when I use "View(dev) - but it comes up with error
> 'dev not found'. How can i fix this? Also is there anyway instead of me
> making a new dataset called "dev" with the 3 columns, I can just re-use my
> original dataset "sub" and give me all the 3 new columns?
>
> The next step I want to do is to perform a cumulative sum. So looking at
> the results, I want a new coloumn in existing dataset (or new dataset),
> which will now have 4 columns. The 4th column I want to be called "CuSum".
> So the first row of Cusum will be "-0.55", the second = "-0.55+(-2.01)"
> which will give me "-2.56" and so on forth.
>
> How can I do this in R using a function? Please help
>
>
>
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