[R] Using if, else statements

[Gabriela Cendoya]

Hi Robin:
                I think you can avoid the loops doing this:

my.df<-data.frame(d.o.w=sample(c("mon","sat","sun"), 20, replace=T),
       admissions=rnorm(20))
weight <- c(1,1,1,1,1,1.21,1.22)
names(weight) <- c("mon","tue","wed","thu","fri","sat","sun")
my.df$NewAdm <- my.df$admissions * weight[as.character(my.df$d.o.w)]

my.df

Gabriela



----- Original Message ----- 
From: "Robin Williams" <robster3 at hotmail.com>
To: <r-help at r-project.org>
Sent: Wednesday, July 23, 2008 12:44 PM
Subject: [R] Using if, else statements


> Hi all,
>
> Again I have searched the net and so on, without finding an answer to this
> surely simple problem. A short bit of code would be appreciated.
>
>  I have a object named `data' with the following column headings.
>
> Date, maxitemp, minitemp, admissions, d.o.w.
>
> Where d.o.w. is day of the week, written "Sun" "Mon" etc.
>
>  I just need to scale the Monday admissions by 0.91, the Saturday
> admissions by 1.21 and the Sunday admissions by 1.22. So basically what I
> want is:
>
> If d.o.w. == "Sat"
>
> Multiply Sat admissions by 1.21.
>
> (Now do I need an else statement here, or can I just do another)
>
> If d.o.w. == "Sun"
>
> Multiply "Sun" admissions by 1.22
>
> (and finally)
>
> If d.o.w. == "Mon"
>
> Multiply Monday admissions by 0.91.
>
> Else do nothing.
>
>  I assume in my code I need to specify that I am using the data.frame
> `data', so do I need to write things like
>
> If(data[d.o.w.]=="Mon")
>
>  I would then like to round the new admissions to integers (I assume I 
> just
> use round(data$admissions)), and output the new data to another csv file.
>
>  I could of course do this in excel but I will need to extend this type of
> idea in the future so I would like to master it in R.
>
> Many thanks for any help/code.
>
> Robin Williams.
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code. 

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