R help - Dec 2009 - apply loop - using/providing a data frame to loop over

Hi,

I want to extract individual names from a single string that contains all
names. My problem is not the extraction itself, but the looping over the
extraction start and end points, which I try to realize with apply.

#Say, I have a string with names.
authors=c("Schleyer T, Spallek H, Butler BS, Subramanian S, Weiss D,
Poythress ML, Rattanathikun P, Mueller G")

#Since I only want the surname and the initial of the first name, I create
respective indices
starts=c(1, 13, 24, 35, 50, 59, 73, 90)
ends=c(10, 21, 31, 47, 56, 69, 87, 98)

#Now I can extract the names, e.g. the third one, with
substr(authors,start=starts[3],stop=ends[3])

#So far so good, but I want to loop over all indices using apply
#For that I wrote a function g, that takes "a" as the author string,
and
"data" as the start and end points for extraction
g=function(a,data){substr(a,data[,1],data[,2])}

#If provided with a specific row of the data frame, g works
g(authors,data.frame(starts,ends)[3,])

#If I try to loop g through the rows of the starts/ends data frame, it does
not work.
apply(data.frame(starts,ends),1,g,a=authors)

#Interestingly, if the data frame to loop over is just a vector, it works
also (e.g. for extracting just the first initial)
g=function(e,a){substr(a,e,e)}
apply(data.frame(ends),1,g,a=authors)

So the problem probably lies in correctly supplying "apply" with the
data
frame. I would greatly appreciate your help.

Daniel

-----------------------------------------------
"Who has visions should see a doctor," 
Helmut Schmidt, German Chancellor (1974-1982).

Try this. It picks out each string of word characters (\w+) followed
by a space followed by a word character:
> library(gsubfn)
> strapply(authors, "\\w+ \\w", c)[[1]]
[1] "Schleyer T"      "Spallek H"       "Butler B"
"Subramanian S"
[5] "Weiss D"         "Poythress M"     "Rattanathikun
P" "Mueller G"

You might need to adjust the regular expression slightly depending on
what the general case is.  See http://gsubfn.googlecode.com for more.

On Mon, Dec 28, 2009 at 7:46 AM, Daniel Malter <dmalter at gmx.net>
wrote:
> Hi,
>
> I want to extract individual names from a single string that contains all
> names. My problem is not the extraction itself, but the looping over the
> extraction start and end points, which I try to realize with apply.
>
> #Say, I have a string with names.
> authors=c("Schleyer T, Spallek H, Butler BS, Subramanian S, Weiss D,
> Poythress ML, Rattanathikun P, Mueller G")
>
> #Since I only want the surname and the initial of the first name, I create
> respective indices
> starts=c(1, 13, 24, 35, 50, 59, 73, 90)
> ends=c(10, 21, 31, 47, 56, 69, 87, 98)
>
> #Now I can extract the names, e.g. the third one, with
> substr(authors,start=starts[3],stop=ends[3])
>
> #So far so good, but I want to loop over all indices using apply
> #For that I wrote a function g, that takes "a" as the author
string, and
> "data" as the start and end points for extraction
> g=function(a,data){substr(a,data[,1],data[,2])}
>
> #If provided with a specific row of the data frame, g works
> g(authors,data.frame(starts,ends)[3,])
>
> #If I try to loop g through the rows of the starts/ends data frame, it does
> not work.
> apply(data.frame(starts,ends),1,g,a=authors)
>
> #Interestingly, if the data frame to loop over is just a vector, it works
> also (e.g. for extracting just the first initial)
> g=function(e,a){substr(a,e,e)}
> apply(data.frame(ends),1,g,a=authors)
>
> So the problem probably lies in correctly supplying "apply" with
the data
> frame. I would greatly appreciate your help.
>
> Daniel
>
> -----------------------------------------------
> "Who has visions should see a doctor,"
> Helmut Schmidt, German Chancellor (1974-1982).
>
> ______________________________________________
> 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.
>

Try this:

mapply(substr, x = authors, start = starts, stop = ends)

On Mon, Dec 28, 2009 at 10:46 AM, Daniel Malter <dmalter at gmx.net>
wrote:
> Hi,
>
> I want to extract individual names from a single string that contains all
> names. My problem is not the extraction itself, but the looping over the
> extraction start and end points, which I try to realize with apply.
>
> #Say, I have a string with names.
> authors=c("Schleyer T, Spallek H, Butler BS, Subramanian S, Weiss D,
> Poythress ML, Rattanathikun P, Mueller G")
>
> #Since I only want the surname and the initial of the first name, I create
> respective indices
> starts=c(1, 13, 24, 35, 50, 59, 73, 90)
> ends=c(10, 21, 31, 47, 56, 69, 87, 98)
>
> #Now I can extract the names, e.g. the third one, with
> substr(authors,start=starts[3],stop=ends[3])
>
> #So far so good, but I want to loop over all indices using apply
> #For that I wrote a function g, that takes "a" as the author
string, and
> "data" as the start and end points for extraction
> g=function(a,data){substr(a,data[,1],data[,2])}
>
> #If provided with a specific row of the data frame, g works
> g(authors,data.frame(starts,ends)[3,])
>
> #If I try to loop g through the rows of the starts/ends data frame, it does
> not work.
> apply(data.frame(starts,ends),1,g,a=authors)
>
> #Interestingly, if the data frame to loop over is just a vector, it works
> also (e.g. for extracting just the first initial)
> g=function(e,a){substr(a,e,e)}
> apply(data.frame(ends),1,g,a=authors)
>
> So the problem probably lies in correctly supplying "apply" with
the data
> frame. I would greatly appreciate your help.
>
> Daniel
>
> -----------------------------------------------
> "Who has visions should see a doctor,"
> Helmut Schmidt, German Chancellor (1974-1982).
>
> ______________________________________________
> 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.
>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

Works a charme, thanks.

Daniel

-------------------------
cuncta stricte discussurus
-------------------------
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Gabor Grothendieck
Sent: Monday, December 28, 2009 12:34 PM
To: Daniel Malter
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] apply loop - using/providing a data frame to loop over

Try this. It picks out each string of word characters (\w+) followed
by a space followed by a word character:
> library(gsubfn)
> strapply(authors, "\\w+ \\w", c)[[1]]
[1] "Schleyer T"      "Spallek H"       "Butler B"
"Subramanian S"
[5] "Weiss D"         "Poythress M"     "Rattanathikun
P" "Mueller G"

You might need to adjust the regular expression slightly depending on
what the general case is.  See http://gsubfn.googlecode.com for more.

On Mon, Dec 28, 2009 at 7:46 AM, Daniel Malter <dmalter at gmx.net>
wrote:
> Hi,
>
> I want to extract individual names from a single string that contains all
> names. My problem is not the extraction itself, but the looping over the
> extraction start and end points, which I try to realize with apply.
>
> #Say, I have a string with names.
> authors=c("Schleyer T, Spallek H, Butler BS, Subramanian S, Weiss D,
> Poythress ML, Rattanathikun P, Mueller G")
>
> #Since I only want the surname and the initial of the first name, I create
> respective indices
> starts=c(1, 13, 24, 35, 50, 59, 73, 90)
> ends=c(10, 21, 31, 47, 56, 69, 87, 98)
>
> #Now I can extract the names, e.g. the third one, with
> substr(authors,start=starts[3],stop=ends[3])
>
> #So far so good, but I want to loop over all indices using apply
> #For that I wrote a function g, that takes "a" as the author
string, and
> "data" as the start and end points for extraction
> g=function(a,data){substr(a,data[,1],data[,2])}
>
> #If provided with a specific row of the data frame, g works
> g(authors,data.frame(starts,ends)[3,])
>
> #If I try to loop g through the rows of the starts/ends data frame, it
does
> not work.
> apply(data.frame(starts,ends),1,g,a=authors)
>
> #Interestingly, if the data frame to loop over is just a vector, it works
> also (e.g. for extracting just the first initial)
> g=function(e,a){substr(a,e,e)}
> apply(data.frame(ends),1,g,a=authors)
>
> So the problem probably lies in correctly supplying "apply" with
the data
> frame. I would greatly appreciate your help.
>
> Daniel
>
> -----------------------------------------------
> "Who has visions should see a doctor,"
> Helmut Schmidt, German Chancellor (1974-1982).
>
> ______________________________________________
> 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.
>
______________________________________________
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.