Re: [R] How to group by then count?
On Jan 6, 2015, at 3:29 PM, Monnand monn...@gmail.com wrote: Thank you, all! Your replies are very useful, especially Don's explanation! One complaint I have is: the function name (talbe) is really not very informative. Why not? You used the word 'table' in your original post, except as Don noted, you were overthinking the problem. The basic concept is a tabulation of discrete values in a vector, which is a basic analytic method. Using commands like: ??table ??frequency would have led you to the table() function, as well as others. Believe it or not, taking a few minutes to have read/searched An Introduction to R, which is the basic R manual, would have led you to the same solution: http://cran.r-project.org/doc/manuals/r-release/R-intro.html#Frequency-tables-from-factors Regards, Marc Schwartz On Sun Jan 04 2015 at 5:03:47 PM MacQueen, Don macque...@llnl.gov wrote: This seems to me to be a case where thinking in terms of computer programming concepts is getting in the way a bit. Approach it as a data analysis task; the S language (upon which R is based) is designed in part for data analysis so there is a function that does most of the job for you. (I changed your vector of strings to make the result more easily interpreted) x = c(1, 1, 2, 1, 5, 2,'3','5','5','2','2') tmp - table(x) ## counts the number of appearances of each element tmp[tmp==max(tmp)] ## finds which one occurs most often 2 4 Meaning that the element '2' appears 4 times. The table() function should be fast even with long vectors. Here's an example with a vector of length 1 million: foo - table( sample(letters, 1e6, replace=TRUE) ) One of the seminal books on the S language is John M Chambers' Programming with Data -- and I would emphasize the with Data part of that title. -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 1/4/15, 1:02 AM, Monnand monn...@gmail.com wrote: Hi all, I thought this was a very naive problem but I have not found any solution which is idiomatic to R. The problem is like this: Assuming we have vector of strings: x = c(1, 1, 2, 1, 5, 2) We want to count number of appearance of each string. i.e. in vector x, string 1 appears 3 times; 2 appears twice and 5 appears once. Then I want to know which string is the majority. In this case, it is 1. For imperative languages like C, C++ Java and python, I would use a hash table to count each strings where keys are the strings and values are the number of appearance. For functional languages like clojure, there're higher order functions like group-by. However, for R, I can hardly find a good solution to this simple problem. I found a hash package, which implements hash table. However, installing a package simple for a hash table is really annoying for me. I did find aggregate and other functions which operates on data frames. But in my case, it is a simple vector. Converting it to a data frame may be not desirable. (Or is it?) Could anyone suggest me an idiomatic way of doing such job in R? I would be appreciate for your help! -Monnand __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
Re: [R] How to group by then count?
Thank you, all! Your replies are very useful, especially Don's explanation! One complaint I have is: the function name (talbe) is really not very informative. On Sun Jan 04 2015 at 5:03:47 PM MacQueen, Don macque...@llnl.gov wrote: This seems to me to be a case where thinking in terms of computer programming concepts is getting in the way a bit. Approach it as a data analysis task; the S language (upon which R is based) is designed in part for data analysis so there is a function that does most of the job for you. (I changed your vector of strings to make the result more easily interpreted) x = c(1, 1, 2, 1, 5, 2,'3','5','5','2','2') tmp - table(x) ## counts the number of appearances of each element tmp[tmp==max(tmp)] ## finds which one occurs most often 2 4 Meaning that the element '2' appears 4 times. The table() function should be fast even with long vectors. Here's an example with a vector of length 1 million: foo - table( sample(letters, 1e6, replace=TRUE) ) One of the seminal books on the S language is John M Chambers' Programming with Data -- and I would emphasize the with Data part of that title. -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 1/4/15, 1:02 AM, Monnand monn...@gmail.com wrote: Hi all, I thought this was a very naive problem but I have not found any solution which is idiomatic to R. The problem is like this: Assuming we have vector of strings: x = c(1, 1, 2, 1, 5, 2) We want to count number of appearance of each string. i.e. in vector x, string 1 appears 3 times; 2 appears twice and 5 appears once. Then I want to know which string is the majority. In this case, it is 1. For imperative languages like C, C++ Java and python, I would use a hash table to count each strings where keys are the strings and values are the number of appearance. For functional languages like clojure, there're higher order functions like group-by. However, for R, I can hardly find a good solution to this simple problem. I found a hash package, which implements hash table. However, installing a package simple for a hash table is really annoying for me. I did find aggregate and other functions which operates on data frames. But in my case, it is a simple vector. Converting it to a data frame may be not desirable. (Or is it?) Could anyone suggest me an idiomatic way of doing such job in R? I would be appreciate for your help! -Monnand [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
Re: [R] How to group by then count?
Dear Monnad, one possible way would be to use as.factor() and in the summary you would get counts for every level. Like this: x = c(1, 1, 2, 1, 5, 2) summary(as.factor(x)) Cheers, Christian Hi all, I thought this was a very naive problem but I have not found any solution which is idiomatic to R. The problem is like this: Assuming we have vector of strings: x = c(1, 1, 2, 1, 5, 2) We want to count number of appearance of each string. i.e. in vector x, string 1 appears 3 times; 2 appears twice and 5 appears once. Then I want to know which string is the majority. In this case, it is 1. For imperative languages like C, C++ Java and python, I would use a hash table to count each strings where keys are the strings and values are the number of appearance. For functional languages like clojure, there're higher order functions like group-by. However, for R, I can hardly find a good solution to this simple problem. I found a hash package, which implements hash table. However, installing a package simple for a hash table is really annoying for me. I did find aggregate and other functions which operates on data frames. But in my case, it is a simple vector. Converting it to a data frame may be not desirable. (Or is it?) Could anyone suggest me an idiomatic way of doing such job in R? I would be appreciate for your help! -Monnand [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
Re: [R] How to group by then count?
On 04-01-2015, at 10:02, Monnand monn...@gmail.com wrote: Hi all, I thought this was a very naive problem but I have not found any solution which is idiomatic to R. The problem is like this: Assuming we have vector of strings: x = c(1, 1, 2, 1, 5, 2) We want to count number of appearance of each string. i.e. in vector x, string 1 appears 3 times; 2 appears twice and 5 appears once. Then I want to know which string is the majority. In this case, it is 1. For imperative languages like C, C++ Java and python, I would use a hash table to count each strings where keys are the strings and values are the number of appearance. For functional languages like clojure, there're higher order functions like group-by. However, for R, I can hardly find a good solution to this simple problem. I found a hash package, which implements hash table. However, installing a package simple for a hash table is really annoying for me. I did find aggregate and other functions which operates on data frames. But in my case, it is a simple vector. Converting it to a data frame may be not desirable. (Or is it?) Could anyone suggest me an idiomatic way of doing such job in R? I would be appreciate for your help! Have a look at table: ?table Berend __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
Re: [R] How to group by then count?
This seems to me to be a case where thinking in terms of computer programming concepts is getting in the way a bit. Approach it as a data analysis task; the S language (upon which R is based) is designed in part for data analysis so there is a function that does most of the job for you. (I changed your vector of strings to make the result more easily interpreted) x = c(1, 1, 2, 1, 5, 2,'3','5','5','2','2') tmp - table(x) ## counts the number of appearances of each element tmp[tmp==max(tmp)] ## finds which one occurs most often 2 4 Meaning that the element '2' appears 4 times. The table() function should be fast even with long vectors. Here's an example with a vector of length 1 million: foo - table( sample(letters, 1e6, replace=TRUE) ) One of the seminal books on the S language is John M Chambers' Programming with Data -- and I would emphasize the with Data part of that title. -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 1/4/15, 1:02 AM, Monnand monn...@gmail.com wrote: Hi all, I thought this was a very naive problem but I have not found any solution which is idiomatic to R. The problem is like this: Assuming we have vector of strings: x = c(1, 1, 2, 1, 5, 2) We want to count number of appearance of each string. i.e. in vector x, string 1 appears 3 times; 2 appears twice and 5 appears once. Then I want to know which string is the majority. In this case, it is 1. For imperative languages like C, C++ Java and python, I would use a hash table to count each strings where keys are the strings and values are the number of appearance. For functional languages like clojure, there're higher order functions like group-by. However, for R, I can hardly find a good solution to this simple problem. I found a hash package, which implements hash table. However, installing a package simple for a hash table is really annoying for me. I did find aggregate and other functions which operates on data frames. But in my case, it is a simple vector. Converting it to a data frame may be not desirable. (Or is it?) Could anyone suggest me an idiomatic way of doing such job in R? I would be appreciate for your help! -Monnand [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
