element wise pattern recognition and string substitution

Hi Ista,

Thanks for the suggestion. I didn't know mapply can be used this way! Let me
take one more step. Instead of defining a pattern for each string, I would
like to define a set of patterns from all the possible combination of the
unique values of those variables. Then I need each string to find a pattern
for itself.

suggestion/comments from everyone.

Jun

On Tue, Sep 6, 2016 at 9:44 PM, Ista Zahn <istazahn at gmail.com> wrote:

If you want to mach each element of 'strings' to a different regex, do
it. Here are three ways, using your original example.

pattern1 <- "([^.]*)\\.([^.]*\\.[^.]*)\\.(.*)"
pattern2 <- "([^.]*)\\.([^.]*)\\.(.*)"

patterns <- c(pattern1,pattern2)
strings <- c('TX.WT.CUT.mean','mg.tx.cv')

for(i in seq(strings)) print(sub(patterns[i], "\\2", strings[i]))

mapply(sub, pattern = patterns, x = strings, MoreArgs=list(replacement =
"\\2"))

library(stringi)
stri_replace_all_regex(strings, patterns, "$2")

Best,
Ista
On Tue, Sep 6, 2016 at 9:20 PM, Jun Shen <jun.shen.ut at gmail.com> wrote:

Hi Jeff,

Thanks for the reply. I tried your suggestion and it doesn't seem to
work
and I tried a simple pattern as follows and it works as expected

sub("(3\\.mg\\.kg)\\.(>50-70\\.kg)\\.(.*)", '\\1',
"3.mg.kg.>50-70.kg.P05")
[1] "3.mg.kg"

sub("(3\\.mg\\.kg)\\.(>50-70\\.kg)\\.(.*)", '\\2',
"3.mg.kg.>50-70.kg.P05")
[1] ">50-70.kg"

sub("(3\\.mg\\.kg)\\.(>50-70\\.kg)\\.(.*)", '\\3',
"3.mg.kg.>50-70.kg.P05")
[1] "P05"

My problem is the pattern has to be dynamically constructed on the input
data of the function I am writing. It's actually not too difficult to
assemble the final.pattern with some code like the following

sort.var <- c('TX','WTCUT')
combn.sort.var <- do.call(expand.grid, lapply(sort.var,

function(x)paste('(',gsub('\\.','\\\\.',unlist(unique(all.exposure[x]))),
')', sep='')))
all.patterns <- do.call(paste, c(combn.sort.var, '(.*)', sep='\\.'))
final.pattern <- paste0(all.patterns, collapse='|')

You cannot run the code directly since the data object "all.exposure" is
not provided here.

Jun



On Tue, Sep 6, 2016 at 8:18 PM, Jeff Newmiller
<jdnewmil at dcn.davis.ca.us>
wrote:

I am not near my computer today, but each parenthesis gets its own
result
number, so you should put the parenthesis around the whole pattern of
alternatives instead of having many parentheses.

I recommend thinking in terms of what common information you expect to
find in these various strings, and place your parentheses to capture
that
information. There is no other reason to put parentheses in the
pattern...
they are not grouping symbols.
--
Sent from my phone. Please excuse my brevity.

On September 6, 2016 5:01:04 PM PDT, Bert Gunter
<bgunter.4567 at gmail.com>
wrote:

Jun:

1. Tell us your desired result from your test vector and maybe someone
will help.

2. As we played this game once already (you couldn't do it; I showed
you how), this seems to be a function of your limitations with regular
expressions. I'm probably not much better, but in any case, I don't
intend to be your consultant. See if you can find someone locally to
help you if you do not receive a satisfactory reply from the list.
There are many people here who are pretty good at this sort of thing,
but I don't know if they'll reply. Regex's are certainly complex. PERL
people tend to be pretty good at them, I believe. There are numerous
web sites and books on them if you need to acquire expertise for your
work.

Cheers,
Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Tue, Sep 6, 2016 at 3:59 PM, Jun Shen <jun.shen.ut at gmail.com>
wrote:

Hi Bert,

I still couldn't make the multiple patterns to work. Here is an

example. I

make the pattern as follows

final.pattern <-

"(240\\.m\\.g)\\.(>50-70\\.kg)\\.(.*)|(3\\.mg\\.kg)\\.(>

50-70\\.kg)\\.(.*)|(240\\.m\\.g)\\.(>70-90\\.kg)\\.(.*)|(3\\
.mg\\.kg)\\.(>70-90\\.kg)\\.(.*)|(240\\.m\\.g)\\.(>90-110\\.
kg)\\.(.*)|(3\\.mg\\.kg)\\.(>90-110\\.kg)\\.(.*)|(240\\.m\\
.g)\\.(50\\.kg\\.or\\.less)\\.(.*)|(3\\.mg\\.kg)\\.(50\\.kg\
\.or\\.less)\\.(.*)|(240\\.m\\.g)\\.(>110\\.kg)\\.(.*)|(3\\.
mg\\.kg)\\.(>110\\.kg)\\.(.*)"

test.string <- c('240.m.g.>110.kg.geo.mean', '3.mg.kg.>110.kg.P05',
'240.m.g.>50-70.kg.geo.mean')

sub(final.pattern, '\\1', test.string)
sub(final.pattern, '\\2', test.string)
sub(final.pattern, '\\3', test.string)

Only the third string has been correctly parsed, which matches the

first

pattern. It seems the rest of the patterns are not called.

Jun


On Mon, Sep 5, 2016 at 10:21 PM, Bert Gunter
<bgunter.4567 at gmail.com>

wrote:

Just noticed: My clumsy do.call() line in my previously posted code
below should be replaced with:
pat <- paste(pat,collapse = "|")

pat <- c(pat1,pat2)
paste(pat,collapse="|")

[1] "a+\\.*a+|b+\\.*b+"

************ replace this **************************

pat <- do.call(paste,c(as.list(pat), sep="|"))

********************************************

sub(paste0("^[^b]*(",pat,").*$"),"\\1",z)

[1] "a.a"   "bb"    "b.bbb"


-- Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming

along

and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Mon, Sep 5, 2016 at 12:11 PM, Bert Gunter

<bgunter.4567 at gmail.com>

wrote:

Jun:

You need to provide a clear specification via regular expressions

of

the patterns you wish to match -- at least for me to decipher it.
Others may be smarter than I, though...

Jeff: Thanks. I have now convinced myself that it can be done (a
"proof" of sorts): If pat1, pat2,..., patn are m different

patterns

(in a vector of patterns)  to be matched in a vector of n
strings,
where only one of the patterns will match in any string,  then
use
paste() (probably via do.call()) or otherwise to paste them

together

separated by "|" to form the concatenated pattern, pat. Then

sub(paste0("^.*(",pat, ").*$"),"\\1",thevector)

should extract the matching pattern in each (perhaps with a
little
fiddling due to precedence rules); e.g.

z <-c(".fg.h.g.a.a", "bb..dd.ef.tgf.", "foo...b.bbb.tgy")

pat1 <- "a+\\.*a+"
pat2 <-"b+\\.*b+"
pat <- c(pat1,pat2)

pat <- do.call(paste,c(as.list(pat), sep="|"))
pat

[1] "a+\\.*a+|b+\\.*b+"

sub(paste0("^[^b]*(",pat,").*$"), "\\1", z)

[1] "a.a"   "bb"    "b.bbb"

Cheers,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming

along

and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip
)


On Mon, Sep 5, 2016 at 9:56 AM, Jun Shen <jun.shen.ut at gmail.com>

wrote:

Thanks for the reply, Bert.

Your solution solves the example. I actually have a more general
situation
where I have this dot concatenated string from multiple

variables. The

problem is those variables may have values with dots in there.

The

number of
dots are not consistent for all values of a variable. So I am

thinking

to
define a vector of patterns for the vector of the string and

hopefully

to
find a way to use a pattern from the pattern vector for each

value of

the
string vector. The only way I can think of is "for" loop, which

can be

slow.
Also these are happening in a function I am writing. Just wonder

if

there is
another more efficient way. Thanks a lot.

Jun

On Mon, Sep 5, 2016 at 1:41 AM, Bert Gunter

<bgunter.4567 at gmail.com>

wrote:

Well, he did provide an example, and...

z <- c('TX.WT.CUT.mean','mg.tx.cv')

sub("^.+?\\.(.+)\\.[^.]+$","\\1",z)

[1] "WT.CUT" "tx"


## seems to do what was requested.

Jeff would have to amplify on his initial statement however: do

you

mean that separate patterns can always be combined via "|" ?
Or
something deeper?

Cheers,
Bert
Bert Gunter

"The trouble with having an open mind is that people keep
coming

along

and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic
strip

)

On Sun, Sep 4, 2016 at 9:30 PM, Jeff Newmiller
<jdnewmil at dcn.davis.ca.us>
wrote:

Your opening assertion is false.

Provide a reproducible example and someone will demonstrate.
--
Sent from my phone. Please excuse my brevity.

On September 4, 2016 9:06:59 PM PDT, Jun Shen
<jun.shen.ut at gmail.com>
wrote:

Dear list,

I have a vector of strings that cannot be described by one

pattern.

So
let's say I construct a vector of patterns in the same length

as the

vector
of strings, can I do the element wise pattern recognition and

string

substitution.

For example,

pattern1 <- "([^.]*)\\.([^.]*\\.[^.]*)\\.(.*)"
pattern2 <- "([^.]*)\\.([^.]*)\\.(.*)"

patterns <- c(pattern1,pattern2)
strings <- c('TX.WT.CUT.mean','mg.tx.cv')

Say I want to extract "WT.CUT" from the first string and "tx"

from

the
second string. If I do

sub(patterns, '\\2', strings), only the first pattern will be

used.

looping the patterns doesn't work the way I want. Appreciate

any

comments.
Thanks.

Jun

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