R help - Jul 2010 - Arrange values on a timeline

I have a set of labels arranged along a timeframe in a. Each label has
a timestamp and marks a state until the next label. The dataframe a
contains 5 such timestamps and 5 associated labels. This means, on a
continious scale between 1-100, there are 5 markers. E.g. 'abc' marks
the timestampls between 10 and 19, 'def' marks the timestamps between
20 and 32, and so on.

a <- data.frame(timestamp=c(3,5,8),
mylabel=c("abc","def","ghi"))
b <- data.frame(timestamp=c(1:10))

I would like to assign these labels as an extra collumn 'label' to the
data.frame b which currently only consists of a the timestamp. The
output would then look like this:

       timestamp      label
1     1                    NA
2     2                    NA
3     3                    "abc"
4     4                    "abc"
5     5                    "def"
6     6                    "def"
7     7                    "def"
8     8                    "ghi"
9     9                    "ghi"
10  10                    "ghi"

What is the simplest way to assign these labels based on timestamps to
get this output. The real dataset is several millions of rows...

Thanks,
Ralf

Try this:

a <- data.frame(timestamp=c(3,5,8),
mylabel=c("abc","def","ghi"))
b <- data.frame(timestamp=c(1:10))

txt <- as.character(a$mylabel)

nrepeat <- diff(c(a$timestamp,nrow(b)))

b$mylabel <-  c( rep(NA, a$timestamp[1]),  rep(txt,
diff(c(a$timestamp,nrow(b)))) )



greetings,
Remko



-------------------------------------------------
Remko Duursma
Research Lecturer

Centre for Plants and the Environment
University of Western Sydney
Hawkesbury Campus
Richmond NSW 2753

Dept of Biological Science
Macquarie University
North Ryde NSW 2109
Australia

Mobile: +61 (0)422 096908
www.remkoduursma.com



On Wed, Jul 14, 2010 at 3:04 PM, Ralf B <ralf.bierig at gmail.com>
wrote:
> I have a set of labels arranged along a timeframe in a. Each label has
> a timestamp and marks a state until the next label. The dataframe a
> contains 5 such timestamps and 5 associated labels. This means, on a
> continious scale between 1-100, there are 5 markers. E.g. 'abc'
marks
> the timestampls between 10 and 19, 'def' marks the timestamps
between
> 20 and 32, and so on.
>
> a <- data.frame(timestamp=c(3,5,8),
mylabel=c("abc","def","ghi"))
> b <- data.frame(timestamp=c(1:10))
>
> I would like to assign these labels as an extra collumn 'label' to
the
> data.frame b which currently only consists of a the timestamp. The
> output would then look like this:
>
> ? ? ? timestamp ? ? ?label
> 1 ? ? 1 ? ? ? ? ? ? ? ? ? ?NA
> 2 ? ? 2 ? ? ? ? ? ? ? ? ? ?NA
> 3 ? ? 3 ? ? ? ? ? ? ? ? ? ?"abc"
> 4 ? ? 4 ? ? ? ? ? ? ? ? ? ?"abc"
> 5 ? ? 5 ? ? ? ? ? ? ? ? ? ?"def"
> 6 ? ? 6 ? ? ? ? ? ? ? ? ? ?"def"
> 7 ? ? 7 ? ? ? ? ? ? ? ? ? ?"def"
> 8 ? ? 8 ? ? ? ? ? ? ? ? ? ?"ghi"
> 9 ? ? 9 ? ? ? ? ? ? ? ? ? ?"ghi"
> 10 ?10 ? ? ? ? ? ? ? ? ? ?"ghi"
>
> What is the simplest way to assign these labels based on timestamps to
> get this output. The real dataset is several millions of rows...
>
> Thanks,
> Ralf
>
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