R help - Dec 2013 - data frame question

Dear All

please help with the following:

I have:

a <-seq(0,10,by=1)
b <-c(10:20)
d <-cbind(a,b)
f <-16

I would like to select the value in column a based on a value in column b, where
the value in column b is the 1st value that is smaller then f. Thus I should end
up with the number 5 because the 1st value that is below 16 would be 15, and in
the same row column a has the number 5.... 

appreciate your insights,

andras
	[[alternative HTML version deleted]]

Thank you for providing a reproducible example. I tweaked it a little
bit to make it actually a data frame problem.

There are lots of ways to do this; here's one approach.

On second thought, this looks a lot like homework, so perhaps instead
I'll just suggest using subset() with more than one condition.

Sarah

On Mon, Dec 9, 2013 at 3:27 PM, Andras Farkas <motyocska at yahoo.com>
wrote:
> Dear All
>
> please help with the following:
>
> I have:
>
> a <-seq(0,10,by=1)
> b <-c(10:20)
> d <-cbind(a,b)
> f <-16
>
> I would like to select the value in column a based on a value in column b,
where the value in column b is the 1st value that is smaller then f. Thus I
should end up with the number 5 because the 1st value that is below 16 would be
15, and in the same row column a has the number 5....
>
> appreciate your insights,
>
> andras
-- 
Sarah Goslee
http://www.functionaldiversity.org

If it's not homework, then I'm happy to provide more help:


a <-seq(0,10,by=1)
b <-c(10:20)
d <-data.frame(a=a,b=b)
f <-16

subset(d, b < f & b == max(b[b < f]))$a

# I'd turn it into a function
getVal <- function(d, f) {
    subset(d, b < f & b == max(b[b < f]))$a
}


Sarah


On Mon, Dec 9, 2013 at 3:50 PM, Andras Farkas <motyocska at yahoo.com>
wrote:
> Sarah,
>
> thank you, not homework though, I guess it just looks like it.... I will
> look into subset()
>
> Andras
>
>
> On Monday, December 9, 2013 3:45 PM, Sarah Goslee <sarah.goslee at
gmail.com>
> wrote:
> Thank you for providing a reproducible example. I tweaked it a little
> bit to make it actually a data frame problem.
>
> There are lots of ways to do this; here's one approach.
>
> On second thought, this looks a lot like homework, so perhaps instead
> I'll just suggest using subset() with more than one condition.
>
> Sarah
>
> On Mon, Dec 9, 2013 at 3:27 PM, Andras Farkas <motyocska at
yahoo.com> wrote:
>> Dear All
>>
>> please help with the following:
>>
>> I have:
>>
>> a <-seq(0,10,by=1)
>> b <-c(10:20)
>> d <-cbind(a,b)
>> f <-16
>>
>> I would like to select the value in column a based on a value in column
b,
>> where the value in column b is the 1st value that is smaller then f.
Thus I
>> should end up with the number 5 because the 1st value that is below 16
would
>> be 15, and in the same row column a has the number 5....
>>
>> appreciate your insights,
>>
>> andras
>

-- 
Sarah Goslee
http://www.functionaldiversity.org