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Extract columns with a string in column name of an R data frame.
To extract columns with a particular string in column name of an R data frame, we can use grepl function for column names and then subset the data frame with single square brackets.
For Example, if we have a data frame called df and we want to extract columns that has X in their names then we can use the command mentioned below −
df[grepl("X",colnames(df))]Example 1
Following snippet creates a sample data frame −
Students_Score<-sample(1:50,20) Teachers_Rank<-sample(1:5,20,replace=TRUE) Teachers_Score<-sample(1:50,20) df1<-data.frame(Students_Score,Teachers_Rank,Teachers_Score) df1
The following dataframe is created
Students_Score Teachers_Rank Teachers_Score 1 37 3 42 2 50 4 15 3 8 5 21 4 29 3 35 5 10 5 3 6 2 2 41 7 12 4 29 8 1 4 44 9 41 2 10 10 39 3 39 11 27 3 43 12 18 1 48 13 44 5 12 14 21 4 16 15 16 3 20 16 45 5 50 17 17 1 31 18 49 1 30 19 47 5 17 20 32 5 8
To extract columns of df1 that contains Score in column name on the above created data frame, add the following code to the above snippet −
Students_Score<-sample(1:50,20)
Teachers_Rank<-sample(1:5,20,replace=TRUE)
Teachers_Score<-sample(1:50,20)
df1<-data.frame(Students_Score,Teachers_Rank,Teachers_Score)
df1[grepl("Score",colnames(df1))]
Output
If you execute all the above given snippets as a single program, it generates the following Output −
Students_Score Teachers_Score 1 37 42 2 50 15 3 8 21 4 29 35 5 10 3 6 2 41 7 12 29 8 1 44 9 41 10 10 39 39 11 27 43 12 18 48 13 44 12 14 21 16 15 16 20 16 45 50 17 17 31 18 49 30 19 47 17 20 32 8
Example 2
Following snippet creates a sample data frame −
Hot_Temp<-sample(33:50,20,replace=TRUE)
Cold_Temp<-sample(1:10,20,replace=TRUE)
Group<-sample(c("First","Second","Third"),20,replace=TRUE)
df2<-data.frame(Hot_Temp,Cold_Temp,Group)
df2
The following dataframe is created
Hot_Temp Cold_Temp Group 1 47 4 Third 2 33 5 First 3 36 2 Second 4 35 8 Second 5 33 8 First 6 44 1 Third 7 33 8 Third 8 46 3 First 9 36 3 Third 10 44 6 First 11 43 10 Third 12 35 9 First 13 36 4 Third 14 44 5 Second 15 48 5 Second 16 37 6 Second 17 35 5 Second 18 42 4 First 19 40 4 Second 20 42 4 Third
To extract columns of df2 that contains Temp in column name on the above created data frame, add the following code to the above snippet −
Hot_Temp<-sample(33:50,20,replace=TRUE)
Cold_Temp<-sample(1:10,20,replace=TRUE)
Group<-sample(c("First","Second","Third"),20,replace=TRUE)
df2<-data.frame(Hot_Temp,Cold_Temp,Group)
df2[grepl("Temp",colnames(df2))]Output
If you execute all the above given snippets as a single program, it generates the following Output −
Hot_Temp Cold_Temp 1 47 4 2 33 5 3 36 2 4 35 8 5 33 8 6 44 1 7 33 8 8 46 3 9 36 3 10 44 6 11 43 10 12 35 9 13 36 4 14 44 5 15 48 5 16 37 6 17 35 5 18 42 4 19 40 4 20 42 4
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