[R] loops and if statements

[Laura Ferrero-Miliani]

Thank you so much all!
How a simple problem can get complicated by not having enough
knowledge, but hopefully I am learning

Have a great Sunday!


L

On Sun, Apr 18, 2010 at 4:56 PM, jim holtman <jholtman at gmail.com> wrote:
> You are working with a matrix, so the "$" operator is not allowed (e.g.,
> d$c).
>
> Also in your test, you have to test against the second column (e.g., d[i,
> 2])
>
> try this:
>
>> a <- c(1:4)
>> b <- c("meep", "foo", "meep", "foo")
>> d <- cbind(a, b)
>>
>>
>> for(i in seq(along=d[,2])) {if (d[i,2]=="meep") { print("oops")}
> +                                    else { print("yay")}
> + }
> [1] "oops"
> [1] "yay"
> [1] "oops"
> [1] "yay"
>>
>> # put results back
>> d <- cbind(d, c=ifelse(d[,2] == 'meep', 'oops', 'yay'))
>> d
>      a   b      c
> [1,] "1" "meep" "oops"
> [2,] "2" "foo"  "yay"
> [3,] "3" "meep" "oops"
> [4,] "4" "foo"  "yay"
>>
>
>
> On Sun, Apr 18, 2010 at 8:46 AM, Laura Ferrero-Miliani <laurafe at gmail.com>
> wrote:
>>
>> Hello,
>> I am very new to R and data analysis in general.
>> I am trying to generate values to append to my data frame using
>> conditional statements.
>> I am playing with this simple example:
>>
>> a <- c(1:4)
>> b <- c("meep", "foo", "meep", "foo")
>> d <- cbind(a, b)
>>
>> now what I want to do is , each time there is a "meep" in column 2 of
>> d, print "oops", else print "yay".
>> So I wrote:
>>
>> for(i in seq(along=d[,2])) {if (d[i]=="meep") { print("oops")}
>>                                    else { print("yay")}
>> }
>>
>> Result:
>> [1] "yay"
>> [1] "yay"
>> [1] "yay"
>> [1] "yay"
>>
>> What am I doing wrong?
>>
>> Furthermore, I would like to append the results to d:
>>
>> d$c <- for(i in seq(along=d[,2])) {if (d[i]=="meep") { print("oops")}
>>                                    else { print("yay")}
>> }
>>
>>
>> this doesn't really work, it just turns the whole thing into a list.
>> .
>> Although if:
>>
>> c <- NA
>> d <- cbind(a, b, c)
>>
>> and I coerce d into a data.frame, run:
>>
>> d$c <- for(i in seq(along=d[,2])) {if (d[i]=="meep") { print("oops")}
>>                                    else { print("yay")}
>> }
>>
>>
>> some glint of hope appears:
>>
>>
>> [1] "yay"
>> [1] "oops"
>>
>> but then......
>>
>>
>>
>> Error in if (d[i] == "meep") { : missing value where TRUE/FALSE needed
>> In addition: Warning messages:
>> 1: In if (d[i] == "meep") { :
>>  the condition has length > 1 and only the first element will be used
>> 2: In if (d[i] == "meep") { :
>>  the condition has length > 1 and only the first element will be used
>> 3: In if (d[i] == "meep") { :
>>  the condition has length > 1 and only the first element will be used
>>
>>
>> To complicate things a little bit more in my real data there are 16
>> levels, so for each level I need to "print" a different value (that
>> would be 16 nested ifs, and I am sure there must be a more sensible
>> way to do this!)
>>
>>
>> Thanks in advance,
>>
>> Laura
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
>
>
> --
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
>
> What is the problem that you are trying to solve?
>