- Trending Categories
Data Structure
Networking
RDBMS
Operating System
Java
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
How to select top rows of an R data frame based on groups of factor column?
We use head function to take a look at some top values in an R data frame but it shows the top values for the whole data frame without considering the groups of factor column. Therefore, if we have a large number of values in a particular group then head function does not seem to be helpful alone, we must use something to extract the top values for each of the groups. This can be done through using by function with single square brackets and head function.
Examples
data(iris) str(iris) 'data.frame': 150 obs. of 5 variables: $ Sepal.Length: num 5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ... $ Sepal.Width : num 3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ... $ Petal.Length: num 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ... $ Petal.Width : num 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ... $ Species : Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 1 1 1 1 1 ... Top5_Based_on_Species<-by(iris,iris["Species"],head,n=5) Top5_Based_on_Species Species: setosa
Output
Sepal.Length Sepal.Width Petal.Length Petal.Width Species 1 5.1 3.5 1.4 0.2 setosa 2 4.9 3.0 1.4 0.2 setosa 3 4.7 3.2 1.3 0.2 setosa 4 4.6 3.1 1.5 0.2 setosa 5 5.0 3.6 1.4 0.2 setosa ------------------------------------------------------------ Species: versicolor Sepal.Length Sepal.Width Petal.Length Petal.Width Species 51 7.0 3.2 4.7 1.4 versicolor 52 6.4 3.2 4.5 1.5 versicolor 53 6.9 3.1 4.9 1.5 versicolor 54 5.5 2.3 4.0 1.3 versicolor 55 6.5 2.8 4.6 1.5 versicolor ------------------------------------------------------------ Species: virginica Sepal.Length Sepal.Width Petal.Length Petal.Width Species 101 6.3 3.3 6.0 2.5 virginica 102 5.8 2.7 5.1 1.9 virginica 103 7.1 3.0 5.9 2.1 virginica 104 6.3 2.9 5.6 1.8 virginica 105 6.5 3.0 5.8 2.2 virginica
Example
data(ToothGrowth) str(ToothGrowth) 'data.frame': 60 obs. of 3 variables: $ len : num 4.2 11.5 7.3 5.8 6.4 10 11.2 11.2 5.2 7 ... $ supp: Factor w/ 2 levels "OJ","VC": 2 2 2 2 2 2 2 2 2 2 ... $ dose: num 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 ... Top10_Based_on_Supp<-by(ToothGrowth,ToothGrowth["supp"],head,n=10) Top10_Based_on_Supp supp: OJ
Output
len supp dose 31 15.2 OJ 0.5 32 21.5 OJ 0.5 33 17.6 OJ 0.5 34 9.7 OJ 0.5 35 14.5 OJ 0.5 36 10.0 OJ 0.5 37 8.2 OJ 0.5 38 9.4 OJ 0.5 39 16.5 OJ 0.5 40 9.7 OJ 0.5 ------------------------------------------------------------ supp: VC len supp dose 1 4.2 VC 0.5 2 11.5 VC 0.5 3 7.3 VC 0.5 4 5.8 VC 0.5 5 6.4 VC 0.5 6 10.0 VC 0.5 7 11.2 VC 0.5 8 11.2 VC 0.5 9 5.2 VC 0.5 10 7.0 VC 0.5
Example
data(CO2) str(CO2) Classes ‘nfnGroupedData’, ‘nfGroupedData’, ‘groupedData’ and 'data.frame': 84 obs. of 5 variables: $ Plant : Ord.factor w/ 12 levels "Qn1"<"Qn2"<"Qn3"<..: 1 1 1 1 1 1 1 2 2 2 ... $ Type : Factor w/ 2 levels "Quebec","Mississippi": 1 1 1 1 1 1 1 1 1 1 ... $ Treatment: Factor w/ 2 levels "nonchilled","chilled": 1 1 1 1 1 1 1 1 1 1 ... $ conc : num 95 175 250 350 500 675 1000 95 175 250 ... $ uptake : num 16 30.4 34.8 37.2 35.3 39.2 39.7 13.6 27.3 37.1 ... - attr(*, "formula")=Class 'formula' language uptake ~ conc | Plant .. ..- attr(*, ".Environment")=<environment: R_EmptyEnv> - attr(*, "outer")=Class 'formula' language ~Treatment * Type .. ..- attr(*, ".Environment")=<environment: R_EmptyEnv> - attr(*, "labels")=List of 2 ..$ x: chr "Ambient carbon dioxide concentration" ..$ y: chr "CO2 uptake rate" - attr(*, "units")=List of 2 ..$ x: chr "(uL/L)" ..$ y: chr "(umol/m^2 s)" Top5_Based_on_Treatment<-by(CO2,CO2["Treatment"],head,n=5) Top5_Based_on_Treatment
Output
Treatment: nonchilled Plant Type Treatment conc uptake 1 Qn1 Quebec nonchilled 95 16.0 2 Qn1 Quebec nonchilled 175 30.4 3 Qn1 Quebec nonchilled 250 34.8 4 Qn1 Quebec nonchilled 350 37.2 5 Qn1 Quebec nonchilled 500 35.3 ------------------------------------------------------------ Treatment: chilled Plant Type Treatment conc uptake 22 Qc1 Quebec chilled 95 14.2 23 Qc1 Quebec chilled 175 24.1 24 Qc1 Quebec chilled 250 30.3 25 Qc1 Quebec chilled 350 34.6 26 Qc1 Quebec chilled 500 32.5
Published on 21-Aug-2020 12:33:01
- Related Questions & Answers
- How to select rows based on range of values of a column in an R data frame?
- How to delete rows of an R data frame based on string match?
- How to add a new column in an R data frame with count based on factor column?
- How to subset rows of an R data frame based on duplicate values in a particular column?
- How to remove rows from an R data frame based on frequency of values in grouping column?
- How to find the column means of a column based on another column values that represent factor in an R data frame?
- How to create bar chart based on two groups in an R data frame?
- How to remove duplicate rows and sort based on a numerical column an R data frame?
- How to find the sum of rows of a column based on multiple columns in R data frame?
- How to get row index based on a value of an R data frame column?
- How to remove rows from data frame in R based on grouping value of a particular column?
- How to remove rows containing missing value based on a particular column in an R data frame?
- How to select the first and last row based on group column in an R data frame?
- Convert a numeric column to binary factor based on a condition in R data frame
- How to select rows of an R data frame that are non-NA?
Advertisements