R regex extract substring followed by end of line or specific character (lazy match)
Question
I have a vector mystr the elements of which contain the unit of measure for a given parameter - this is indicated by the letters, symbols etc. following UOM= . This may be placed at the end of a string or delimited by a semicolon ;
c("\\\\Server-01?6cf038ea-d583-4860-9488-67ee59c767c2\\expnum.2PDT35103?6438;TimeMethod=AtOrBefore;UOM=inHg;pointtype=Float32;displaydigits=1",
"\\\\Server02-01?6cf038ea-d583-4860-9488-67ee59c767c2\\testnum.2BTAVGBARPR.OUT?6449;TimeMethod=AtOrBefore;UOM=inHg",
"\\\\Server02-01?6cf038ea-d583-4860-9488-67ee59c767c2\\testnum3.2PT39248S.XQ01?6453;TimeMethod=AtOrBefore;UOM=psia;pointtype=Float32;displaydigits=1")
In the above example, I'd like to extract inHg , inHg and psia respectively. So far I've tried using regmatches and regexec but haven't found anything that works for all three examples here:
regex_func <- function(string, ptrn){
return(regmatches(x = string, m = regexec(pattern = ptrn, text = string))[[1]][2])
}
> sapply(mystr, function(z){ regex_func(string = z, ptrn = '.*UOM=(.*)[$;]?')}, USE.NAMES = F)
[1] "inHg;pointtype=Float32;displaydigits=1" "inHg"
[3] "psia;pointtype=Float32;displaydigits=1"
> sapply(mystr, function(z){ regex_func(string = z, ptrn = '.*UOM=(.*)[$;]+?')}, USE.NAMES = F)
[1] "inHg" NA "psia"
> sapply(mystr, function(z){ regex_func(string = z, ptrn = '.*UOM=(.*)[$;]')}, USE.NAMES = F)
[1] "inHg;pointtype=Float32" NA "psia;pointtype=Float32"
> sapply(mystr, function(z){ regex_func(string = z, ptrn = '.*UOM=(.*)[$;]{0,1}')}, USE.NAMES = F)
[1] "inHg;pointtype=Float32;displaydigits=1" "inHg"
[3] "psia;pointtype=Float32;displaydigits=1"
I'm not tied to regmatches and am open to using other functions/packages as well eg stringr , stringi
EDIT
Added. sample data Frame with all info - not all ConfigString elements have UOM .
structure(list(Name = c("Ambient Pressure", "Ambient RH", "Ambient Temperature",
"Average Exhaust Gas Temp", "Bellmouth Temperature", "Compressor Discharge Pressure",
"Compressor Discharge Temperature", "Current Power Output", "Degradation in Heat Rate (Comp Effic)",
"Degradation in Power Output (Comp Effic)", "DirtPenetratingToEngineSinceLastWash",
"Fuel Gas Temperature", "Fuel Heating Value (by volume)", "Fuel Volumetric Flow",
"GT Fired Hours", "HRSG HP Steam Outlet Mass Flow", "HRSG HP Steam Outlet Pressure",
"HRSG HP Steam Outlet Temperature", "HRSG IP Steam Outlet Mass Flow",
"HRSG IP Steam Outlet Pressure", "HRSG IP Steam Outlet Temperature",
"HRSG LP Steam Outlet Mass Flow", "HRSG LP Steam Outlet Pressure",
"HRSG LP Steam Outlet Temperature", "Inlet Guide Vane Position",
"Inlet system pressure drop", "Steam Injection Flow", "Steam Injection Pressure",
"Steam Injection Temp"), DefaultUnitsName = c("kilopascal", "percent",
"degree Celsius", "degree Celsius", "degree Celsius", "kilopascal",
"degree Celsius", "megawatt", "kilojoule per kilowatt-hour",
"megawatt", "gram", "degree Celsius", "BTU per standard cubic foot",
"standard cubic foot per second", "hour", "kilogram per second",
"kilopascal", "degree Celsius", "kilogram per second", "kilopascal",
"degree Celsius", "kilogram per second", "kilopascal", "degree Celsius",
"degree", "kilopascal", "kilogram per second", "pound-force per square inch",
"degree Celsius"), DefaultUnitsNameAbbreviation = c("kPa", "%",
"°C", "°C", "°C", "kPa", "°C", "MW", "kJ/kWh", "MW", "g", "°C",
"BTU/scf", "scfs", "h", "kg/s", "kPa", "°C", "kg/s", "kPa", "°C",
"kg/s", "kPa", "°C", "°", "kPa", "kg/s", "psi", "°C"), ConfigString = c("\\\\#\\asset1.2BTAVGBARPR.OUT?6449;TimeMethod=AtOrBefore;UOM=inHg",
"\\\\#\\asset1.2BTAVGHUM.OUT?6423;TimeMethod=AtOrBefore", "\\\\#\\asset1.2BTAVGAMBTEMP.OUT?6446;TimeMethod=AtOrBefore;UOM=°F",
"\\\\#\\asset1.2TEAVTX.ZQ01?6456;TimeMethod=AtOrBefore;UOM=°F",
"\\\\#\\asset1.BT0110.CTGgtAIte01a?6802;TimeMethod=AtOrBefore;UOM=°F;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2PT39248S.XQ01?6453;TimeMethod=AtOrBefore;UOM=psia;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2TE35401S.XQ02?6457;TimeMethod=AtOrBefore;UOM=°F;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2JT38601S.XQ01?6450;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\Degradation in Heat Rate (Comp Effic)?6275;TimeMethod=AtOrBefore",
"\\\\#\\Degradation in Power Output (Comp Effic)?6274;TimeMethod=AtOrBefore",
"\\\\#\\Dust?6273;TimeMethod=AtOrBefore",
"\\\\#\\asset1.2TE36112.XQ01?6454;TimeMethod=AtOrBefore;UOM=°F;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2FC54SUM.XQ01?6448;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.BT0110.CTGgtFGvl01a?6801;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2CTGFiredHours?6800;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2FT5050S.XQ01?6455;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2PT5000S.XQ01?6799;TimeMethod=AtOrBefore;UOM=psi;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2TE5020S.XQ01?6798;TimeMethod=AtOrBefore;UOM=°F;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2FT5150S.XQ01?6447;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2PT5100S.XQ01?6797;UOM=psi;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2TE5120S.XQ01?6796;TimeMethod=AtOrBefore;UOM=°F;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2FT5250S.XQ01?6443;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2PT5200S.XQ01?6795;TimeMethod=AtOrBefore;UOM=psi;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2TE5220S.XQ01?6794;TimeMethod=AtOrBefore;UOM=°F;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2ZT35203.XQ01?6432;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2PDT35103?6438;TimeMethod=AtOrBefore;UOM=inHg;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2FT36602X.ZQ01?6792;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2PT245.XQ01?6793;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1",
"\\\\#\\asset1.2TE240.XQ01?6791;TimeMethod=AtOrBefore;UOM=°F;pointtype=Float32;displaydigits=1"
)), row.names = c(NA, -29L), class = c("data.table", "data.frame"
))
# 15 items returned
> regmatches(x = dat$ConfigString, regexpr(pattern = '[?;]UOM=\\K[^;]+', text = dat$ConfigString, perl = T))
[1] "inHg" "°F" "°F" "°F" "psia" "°F" "°F" "psi" "°F" "psi" "°F" "psi" "°F" "inHg" "°F"
Using the chosen solution with this data:
# operation on a vector
> dat[, uom := regmatches(ConfigString, regexpr(pattern = '[?;]UOM=\\K[^;]+', ConfigString, perl = T))]
# using := operator in data.table
> dat[, uom := regmatches(ConfigString, regexpr(pattern = '[?;]UOM=\\K[^;]+', ConfigString, perl = T))]
Error in `[.data.table`(dat, , `:=`(uom, regmatches(ConfigString, regexpr(pattern = "[?;]UOM=\\K[^;]+", :
Supplied 15 items to be assigned to 29 items of column 'uom'. If you wish to 'recycle' the RHS please use rep() to make this intent clear to readers of your code.
Using stringr
> stringr::str_replace(dat$ConfigString, ".*[?;]UOM=([^;]+).*", "\\1")
[1] "inHg"
[2] "\\\\#\\asset1.2BTAVGHUM.OUT?6423;TimeMethod=AtOrBefore"
[3] "°F"
[4] "°F"
[5] "°F"
[6] "psia"
[7] "°F"
[8] "\\\\#\\asset1.2JT38601S.XQ01?6450;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[9] "\\\\#\\Degradation in Heat Rate (Comp Effic)?6275;TimeMethod=AtOrBefore"
[10] "\\\\#\\Degradation in Power Output (Comp Effic)?6274;TimeMethod=AtOrBefore"
[11] "\\\\#\\Dust?6273;TimeMethod=AtOrBefore"
[12] "°F"
[13] "\\\\#\\asset1.2FC54SUM.XQ01?6448;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[14] "\\\\#\\asset1.BT0110.CTGgtFGvl01a?6801;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[15] "\\\\#\\asset1.2CTGFiredHours?6800;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[16] "\\\\#\\asset1.2FT5050S.XQ01?6455;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[17] "psi"
[18] "°F"
[19] "\\\\#\\asset1.2FT5150S.XQ01?6447;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[20] "psi"
[21] "°F"
[22] "\\\\#\\asset1.2FT5250S.XQ01?6443;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[23] "psi"
[24] "°F"
[25] "\\\\#\\asset1.2ZT35203.XQ01?6432;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[26] "inHg"
[27] "\\\\#\\asset1.2FT36602X.ZQ01?6792;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[28] "\\\\#\\asset1.2PT245.XQ01?6793;TimeMethod=AtOrBefore;pointtype=Float32;displaydigits=1"
[29] "°F"
1 answers
solution1
0 ACCPTED 2021-01-20 22:00:37
You can use the following base R PCRE regex solution:
[?;]UOM=\K[^;]+
Alternatively, a stringr solution like
library(stringr)
str_match(x, "[?;]UOM=([^;]+)")[,2]
See the regex demo . Details :
-
[?;]- a?or;char UOM=- aUOM=substring-
\K- match reset operator [^;]+- one or more chars other than;char.
See the R demo :
x <- c("\\\\Server-01?6cf038ea-d583-4860-9488-67ee59c767c2\\expnum.2PDT35103?6438;TimeMethod=AtOrBefore;UOM=inHg;pointtype=Float32;displaydigits=1",
"\\\\Server02-01?6cf038ea-d583-4860-9488-67ee59c767c2\\testnum.2BTAVGBARPR.OUT?6449;TimeMethod=AtOrBefore;UOM=inHg",
"\\\\Server02-01?6cf038ea-d583-4860-9488-67ee59c767c2\\testnum3.2PT39248S.XQ01?6453;TimeMethod=AtOrBefore;UOM=psia;pointtype=Float32;displaydigits=1",
"\\\\Server02-01?6cf038ea-d583-4860-9488-67ee59c767c2\\testnum.2TE36112.XQ01?6454;TimeMethod=AtOrBefore;UOM=°F;pointtype=Float32;displaydigits=1")
regmatches(x, regexpr("[?;]UOM=\\K[^;]+", x, perl=TRUE))
## => [1] "inHg" "inHg" "psia" "°F"
library(stringr)
str_match(x, "[?;]UOM=([^;]+)")[,2]
## => [1] "inHg" "inHg" "psia" "°F"
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