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Hello,
You should post a working example, we have no idea what your 2d data set is. A matrix? A data.frame? Something else? And the string you are looking for? Are you thinking of regular expressions (grep) or is it a simple equality '=='? Here is a reproducible example of the use of ?which() with argument arr.ind set to TRUE. # create a data set set.seed(2021) A < matrix(sample(letters, 24, TRUE), ncol = 4) # Test for equality, this returns # a logical matrix and which() can # be applied to it found < A == "g" which(found, arr.ind = TRUE) # row col #[1,] 1 1 #[2,] 5 1 #[3,] 2 3 # The same code can be use if the data is # a data.frame df1 < as.data.frame(A) df1 == "g" But if you want to look for a regex, try sapply. In this example the pattern is a simple one, and I use grepl. pattern < "g" found2 < sapply(df1, function(x) grepl(pattern, x)) which(found2, arr.ind = TRUE) Hope this helps, Rui Barradas Às 18:07 de 15/05/21, Tuhin Chakraborty escreveu: > Hi, > How can I find the location of string data in my 2D dataset? spec(Dataset) > will reveal the columns that contain the strings. But can I know where > exactly the string values are in the column? > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] mailing list  To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/rhelp > PLEASE do read the posting guide http://www.Rproject.org/postingguide.html > and provide commented, minimal, selfcontained, reproducible code. > ______________________________________________ [hidden email] mailing list  To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/rhelp PLEASE do read the posting guide http://www.Rproject.org/postingguide.html and provide commented, minimal, selfcontained, reproducible code. 
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Hello,
The data makes clearer. Do you want to know where are the values that cannot be coerced to numeric? The auxiliary function f outputs a logical vector, sapply applies it column by column and which(., arr.ind) gives the TRUE values as (row, col) pairs. txt < " LI(PPM) SC(PPM) TI(PPM) V(PPM) 3.1/0.5 ? ? ? ? ? 0.2/0.3 ? ? 2.8/0.75 ? >0.2 0.0389 108.6591 0.0214 85.18818 0.0688 146.1739 0.0117 108.0221 0.0265 121.3268 0.00749 85.34932 0.139901 125.3066 0.00984 97.23175 " df1 < read.table(text = txt, header = TRUE) df1 f < function(x){ suppressWarnings(is.na(as.numeric(x))) } found < sapply(df1, f) which(found, arr.ind = TRUE) Hope this helps, Rui Barradas Às 06:31 de 16/05/21, Tuhin Chakraborty escreveu: > Thank you everyone, for the very helpful suggestions. I understand that my > question is not altogether clear. So let me share an example. > The below is a part of a dataset, there are around 40000 rows. > LI(PPM) SC(PPM) TI(PPM) V(PPM) > 3.1/0.5 ? ? ? > ? ? 0.2/0.3 > ? > ? 2.8/0.75 ? >0.2 > 0.0389 108.6591 0.0214 85.18818 > 0.0688 146.1739 0.0117 108.0221 > 0.0265 121.3268 0.00749 85.34932 > 0.139901 125.3066 0.00984 97.23175 > > Now the 0.2/0.3, >0.2 these are treated as strings. When I am using the > spec(Dataset) function in R, it shows me which columns contain strings. > Like it will tell me that LI (PPM), SC(PPM) etc. contain strings. But, I > would like to know if there is someway where I can learn exactly where the > string values are, like for LI(PPM) in the top row. As this is a huge > dataset, it is difficult to go through all the rows manually. > Thank you again and in anticipation. > Tuhin > > > > On Sun, May 16, 2021 at 4:25 AM Avi Gross via Rhelp <[hidden email]> > wrote: > >> Tuhin, >> >> What do you mean by a 2D dataset? You say some columns contain strings so >> it does not sound like you are using a matrix as then ALL columns would be >> of the same type. >> >> So are you using a data.frame or tibble or something you made on your own? >> >> Can you address one column at a time and would that be of type vector? Some >> methods work fairly easily on those and some also on lists. >> >> Once you have that vector, there are quite a few ways to find what you >> want. >> Is it fixed text like looking for an exact full match so it would be >> something like "theta" to be matched in full, or would you want to match >> "the" and both "theta" and "lathe" would match? Or are you matching a >> pattern that is more complex like looking for all text that has two vowels >> in a row in it? >> >> Once you figure out what you have and what you want, how do you want to >> identify what you are looking for? Will there be one match or possibly many >> or even all? Many methods will return a TRUE/FALSE vector of the same >> length >> or the integer offset of a match such as telling you it is the fifth item. >> >> R has collections of string functions including in packages like >> stringr/stringi that deal well with many things you might need. For >> matching >> patterns, there is a family of functions using "grep" and so on. >> >> Good luck. >> >> Original Message >> From: Rhelp <[hidden email]> On Behalf Of Tuhin Chakraborty >> Sent: Saturday, May 15, 2021 1:08 PM >> To: [hidden email] >> Subject: [R] Finding strings in a dataset >> >> Hi, >> How can I find the location of string data in my 2D dataset? spec(Dataset) >> will reveal the columns that contain the strings. But can I know where >> exactly the string values are in the column? >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> [hidden email] mailing list  To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/rhelp >> PLEASE do read the posting guide >> http://www.Rproject.org/postingguide.html >> and provide commented, minimal, selfcontained, reproducible code. >> >> ______________________________________________ >> [hidden email] mailing list  To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/rhelp >> PLEASE do read the posting guide >> http://www.Rproject.org/postingguide.html >> and provide commented, minimal, selfcontained, reproducible code. >> > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] mailing list  To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/rhelp > PLEASE do read the posting guide http://www.Rproject.org/postingguide.html > and provide commented, minimal, selfcontained, reproducible code. > ______________________________________________ [hidden email] mailing list  To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/rhelp PLEASE do read the posting guide http://www.Rproject.org/postingguide.html and provide commented, minimal, selfcontained, reproducible code. 
Hello,
You can also create an extra column with the column names corresponding to the column col. I believe this extra column is not needed and with a big data set it's even a waste of time and memory space but the code below creates it. res < which(found, arr.ind = TRUE) res < as.data.frame(res) res$col_name < names(df1)[ res$col ] With a big data set the first res is a numeric matrix and it's access and extraction is faster, matrix operations are generally faster than data.frame operations. Hope this helps, Rui Barradas Às 08:30 de 16/05/21, Rui Barradas escreveu: > Hello, > > The data makes clearer. > Do you want to know where are the values that cannot be coerced to numeric? > The auxiliary function f outputs a logical vector, sapply applies it > column by column and which(., arr.ind) gives the TRUE values as (row, > col) pairs. > > > txt < " > LI(PPM) SC(PPM) TI(PPM) V(PPM) > 3.1/0.5 ? ? ? > ? ? 0.2/0.3 ? > ? 2.8/0.75 ? >0.2 > 0.0389 108.6591 0.0214 85.18818 > 0.0688 146.1739 0.0117 108.0221 > 0.0265 121.3268 0.00749 85.34932 > 0.139901 125.3066 0.00984 97.23175 > " > df1 < read.table(text = txt, header = TRUE) > df1 > > f < function(x){ > suppressWarnings(is.na(as.numeric(x))) > } > found < sapply(df1, f) > which(found, arr.ind = TRUE) > > > > Hope this helps, > > Rui Barradas > > > Às 06:31 de 16/05/21, Tuhin Chakraborty escreveu: >> Thank you everyone, for the very helpful suggestions. I understand >> that my >> question is not altogether clear. So let me share an example. >> The below is a part of a dataset, there are around 40000 rows. >> LI(PPM) SC(PPM) TI(PPM) V(PPM) >> 3.1/0.5 ? ? ? >> ? ? 0.2/0.3 >> ? >> ? 2.8/0.75 ? >0.2 >> 0.0389 108.6591 0.0214 85.18818 >> 0.0688 146.1739 0.0117 108.0221 >> 0.0265 121.3268 0.00749 85.34932 >> 0.139901 125.3066 0.00984 97.23175 >> >> Now the 0.2/0.3, >0.2 these are treated as strings. When I am using the >> spec(Dataset) function in R, it shows me which columns contain strings. >> Like it will tell me that LI (PPM), SC(PPM) etc. contain strings. But, I >> would like to know if there is someway where I can learn exactly where >> the >> string values are, like for LI(PPM) in the top row. As this is a huge >> dataset, it is difficult to go through all the rows manually. >> Thank you again and in anticipation. >> Tuhin >> >> >> >> On Sun, May 16, 2021 at 4:25 AM Avi Gross via Rhelp >> <[hidden email]> >> wrote: >> >>> Tuhin, >>> >>> What do you mean by a 2D dataset? You say some columns contain >>> strings so >>> it does not sound like you are using a matrix as then ALL columns >>> would be >>> of the same type. >>> >>> So are you using a data.frame or tibble or something you made on your >>> own? >>> >>> Can you address one column at a time and would that be of type >>> vector? Some >>> methods work fairly easily on those and some also on lists. >>> >>> Once you have that vector, there are quite a few ways to find what you >>> want. >>> Is it fixed text like looking for an exact full match so it would be >>> something like "theta" to be matched in full, or would you want to match >>> "the" and both "theta" and "lathe" would match? Or are you matching a >>> pattern that is more complex like looking for all text that has two >>> vowels >>> in a row in it? >>> >>> Once you figure out what you have and what you want, how do you want to >>> identify what you are looking for? Will there be one match or >>> possibly many >>> or even all? Many methods will return a TRUE/FALSE vector of the same >>> length >>> or the integer offset of a match such as telling you it is the fifth >>> item. >>> >>> R has collections of string functions including in packages like >>> stringr/stringi that deal well with many things you might need. For >>> matching >>> patterns, there is a family of functions using "grep" and so on. >>> >>> Good luck. >>> >>> Original Message >>> From: Rhelp <[hidden email]> On Behalf Of Tuhin >>> Chakraborty >>> Sent: Saturday, May 15, 2021 1:08 PM >>> To: [hidden email] >>> Subject: [R] Finding strings in a dataset >>> >>> Hi, >>> How can I find the location of string data in my 2D dataset? >>> spec(Dataset) >>> will reveal the columns that contain the strings. But can I know where >>> exactly the string values are in the column? >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> [hidden email] mailing list  To UNSUBSCRIBE and more, see >>> https://stat.ethz.ch/mailman/listinfo/rhelp >>> PLEASE do read the posting guide >>> http://www.Rproject.org/postingguide.html >>> and provide commented, minimal, selfcontained, reproducible code. >>> >>> ______________________________________________ >>> [hidden email] mailing list  To UNSUBSCRIBE and more, see >>> https://stat.ethz.ch/mailman/listinfo/rhelp >>> PLEASE do read the posting guide >>> http://www.Rproject.org/postingguide.html >>> and provide commented, minimal, selfcontained, reproducible code. >>> >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> [hidden email] mailing list  To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/rhelp >> PLEASE do read the posting guide >> http://www.Rproject.org/postingguide.html >> and provide commented, minimal, selfcontained, reproducible code. >> ______________________________________________ [hidden email] mailing list  To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/rhelp PLEASE do read the posting guide http://www.Rproject.org/postingguide.html and provide commented, minimal, selfcontained, reproducible code. 
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