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Check which column names contain a specific string in R data frame.
If we have a data frame that contains columns having names with some commong strings then we might want to find those column names. For this purpose, we can use grepl function for subsetting along with colnames function.
Check out the Examples given below to understand how it can be done.
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 20 5 8 2 28 1 26 3 42 2 49 4 25 2 11 5 7 4 19 6 4 5 37 7 48 1 9 8 33 4 35 9 23 5 38 10 31 3 29 11 43 1 6 12 6 4 13 13 15 5 33 14 9 1 40 15 41 3 43 16 11 4 34 17 46 5 42 18 44 1 5 19 21 3 48 20 29 4 15
To check columns of df1 that contains string Score 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)
colnames(df1)[grepl("Score",colnames(df1))]Output
If you execute all the above given snippets as a single program, it generates the following Output −
[1] "Students_Score" "Teachers_Score"
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)
df2The following dataframe is created
Hot_Temp Cold_Temp Group 1 47 7 First 2 38 5 Third 3 48 7 Third 4 36 10 First 5 46 6 Third 6 45 2 First 7 35 8 Second 8 33 1 Second 9 33 4 First 10 34 5 First 11 34 6 Third 12 39 10 Third 13 47 10 First 14 41 6 Third 15 48 3 First 16 36 2 Third 17 49 9 Second 18 35 5 Second 19 33 1 Second 20 49 10 Third
To check columns of df2 that contains string Temp 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)
colnames(df2)[grepl("Temp",colnames(df2))]Output
If you execute all the above given snippets as a single program, it generates the following Output −
[1] "Hot_Temp" "Cold_Temp"
Example 3
Following snippet creates a sample data frame −
x1_Rate<-sample(1:10,20,replace=TRUE)
x2_Rate<-sample(1:10,20,replace=TRUE)
Category<-sample(c("Normal","Abnormal"),20,replace=TRUE)
df3<-data.frame(x1_Rate,x2_Rate,Category)
df3The following dataframe is created
x1_Rate x2_Rate Category 1 5 9 Normal 2 8 8 Normal 3 7 10 Normal 4 3 3 Normal 5 6 6 Normal 6 4 9 Abnormal 7 6 5 Abnormal 8 2 9 Abnormal 9 3 10 Abnormal 10 7 4 Abnormal 11 1 3 Normal 12 9 10 Abnormal 13 3 3 Normal 14 8 10 Abnormal 15 3 5 Normal 16 2 5 Abnormal 17 2 1 Normal 18 5 7 Abnormal 19 7 1 Abnormal 20 5 8 Normal
To check columns of df3 that contains string Rate on the above created data frame, add the following code to the above snippet −
x1_Rate<-sample(1:10,20,replace=TRUE)
x2_Rate<-sample(1:10,20,replace=TRUE)
Category<-sample(c("Normal","Abnormal"),20,replace=TRUE)
df3<-data.frame(x1_Rate,x2_Rate,Category)
colnames(df3)[grepl("Rate",colnames(df3))]Output
If you execute all the above given snippets as a single program, it generates the following Output −
[1] "x1_Rate" "x2_Rate"
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