how to merge within range?

On May 14, 2011, at 2:27 PM, William Dunlap wrote:

You could use findInterval() along with a trick with c(rbind(...)):

i <- findInterval(x=df.1$time, vec=c(rbind(df.2$from, df.2$to)))
i

[1] 1 1 1 2 3 3 3 5 5 6

That's nice. I was working on a slightly different "trick"

findInterval( df.1[,1],t(df.2[,1:2]))
 [1] 1 1 1 2 3 3 3 5 5 6

I was then trying to get the right indices with (.)'%%' 2 and (.) '%/%' 2

The even-valued outputs would map to NA's, the odds
to value[(i+1)/2], but you can use the c(rbind(...)) trick again:

c(rbind(df.2$value, NA))[i]

[1]  1  1  1 NA  3  3  3  5  5 NA

I'd like to understand that. Maybe, maybe... ah, got it. At first I  
didn't realize those were the final answers since they looked like  
indices. My t(.) trick doesn't generalize as well.


My earlier suggestion tht two merges woul do it was based on my  
erroneous interpretation of the example, since  I thought the task  
was to match on the end points of the intervals.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

-----Original Message-----
From: r-help-bounces at r-project.org
[mailto:r-help-bounces at r-project.org] On Behalf Of Ren? Mayer
Sent: Saturday, May 14, 2011 11:06 AM
To: David Winsemius
Cc: r-help at r-project.org
Subject: Re: [R] how to merge within range?

thanks David and Ian,
let me make a better example as the first one was flawed

df.1=data.frame(round((1:10)*100+rnorm(10)), value=NA)
names(df.1) = c("time", "value")
df.1
  time value
1   101    NA
2   199    NA
3   301    NA
4   401    NA
5   501    NA
6   601    NA
7   700    NA
8   800    NA
9   900    NA
10 1000    NA

# from and to define ranges within time,
# note that from and to may not match the numbers given in time
df.2=data.frame(from=c(99,500,799),to=c(303,702,950), value=c(1,3,5))
df.2
 from  to value
1   99 303     1
2  500 702     3
3  799 950     5

what I want is:
  time value
1   101    1
2   199    1
3   301    1
4   401    NA
5   501    3
6   601    3
7   700    3
8   800    5
9   900    5
10 1000    NA

@David I don't know what you mean by 2 merges,
Ren?





Zitat von "David Winsemius" <dwinsemius at comcast.net>:

On May 14, 2011, at 9:16 AM, Ian Gow wrote:

If I assume that the third column in data.frame.2 is named

"val" then in

SQL terms it _seems_ you want

SELECT a.time, b.val FROM data.frame.1 AS a LEFT JOIN

data.frame.2 AS b ON

a.time BETWEEN b.start AND b.end;

Not sure how to do that elegantly using R subsetting/merge,

Huh? It's just two merge()'s (... once you fix the error in

the example.)

-- 
David

but you might
try a package that allows you to use SQL, such as sqldf.


On 5/14/11 8:03 AM, "David Winsemius"

<dwinsemius at comcast.net> wrote:

On May 14, 2011, at 8:12 AM, Ren? Mayer wrote:

Hello,
how can one merge

And what happened when you typed:

?merge

two data frames when in the second data frame one column

defines the

start values
and another defines the end value of the to be merged range.
data.frame.1
time ...
13
24
35
46
55
...
data.frame.2
start end
24 37 ?h? ?
...

should result in this
13 NA
24 ?h?
35 ?h?
46 NA
55
?

And _why_ would that be?

thanks,
Ren?

reproducible code.

David Winsemius, MD
West Hartford, CT

David Winsemius, MD
West Hartford, CT

David Winsemius, MD
West Hartford, CT