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Find the row means for columns starting with a string in an R data frame.
To find the row means for columns starting with specific string in an R data frame, we can use mutate function of dplyr package along with rowMeans function.
For Example, if we have a data frame called df that contains three columns say x1_x2, x1_x3, x1_x2 and we want to find the row means for columns x1_x2 and x1_x3 then, we can use the below command −
df%%mutate(X1_Cmbn=select(.,starts_with("x1_")) %% rowMeans())Example 1
Following snippet creates a sample data frame −
Grp1_x<-rpois(20,2) Grp1_y<-rpois(20,5) Grp2_y<-rpois(20,5) Grp2_x<-rpois(20,2) df1<-data.frame(Grp1_x,Grp1_y,Grp2_y,Grp2_x) df1
The following dataframe is created
Grp1_x Grp1_y Grp2_y Grp2_x 1 1 5 4 4 2 1 3 4 2 3 0 4 7 2 4 2 4 2 1 5 1 3 7 3 6 3 5 4 2 7 4 10 6 3 8 5 5 4 2 9 2 2 5 1 10 7 2 3 4 11 1 3 4 3 12 1 5 4 1 13 2 11 7 6 14 3 8 4 1 15 2 7 5 2 16 2 1 3 1 17 3 3 8 2 18 1 2 4 3 19 1 5 7 2 20 0 4 1 2
To load dplyr package and find the row means of columns having Grp1_ in the column name on the above created data frame, add the following code to the above snippet −
Grp1_x<-rpois(20,2)
Grp1_y<-rpois(20,5)
Grp2_y<-rpois(20,5)
Grp2_x<-rpois(20,2)
df1<-data.frame(Grp1_x,Grp1_y,Grp2_y,Grp2_x)
library(dplyr)
df1%%mutate(Group_1=select(.,starts_with("Grp1_")) %% rowMeans())Output
If you execute all the above given snippets as a single program, it generates the following Output −
Grp1_x Grp1_y Grp2_y Grp2_x Group_1 1 1 5 4 4 3.0 2 1 3 4 2 2.0 3 0 4 7 2 2.0 4 2 4 2 1 3.0 5 1 3 7 3 2.0 6 3 5 4 2 4.0 7 4 10 6 3 7.0 8 5 5 4 2 5.0 9 2 2 5 1 2.0 10 7 2 3 4 4.5 11 1 3 4 3 2.0 12 1 5 4 1 3.0 13 2 11 7 6 6.5 14 3 8 4 1 5.5 15 2 7 5 2 4.5 16 2 1 3 1 1.5 17 3 3 8 2 3.0 18 1 2 4 3 1.5 19 1 5 7 2 3.0 20 0 4 1 2 2.0
Example 2
Following snippet creates a sample data frame −
MaleHeight<-sample(150:180,20) MaleWeight<-sample(50:80,20) FemaleHeight<-sample(150:180,20) FemaleWeight<-sample(50:80,20) df2<-data.frame(MaleHeight,MaleWeight,FemaleHeight,FemaleWeight) df2
The following dataframe is created
MaleHeight MaleWeight FemaleHeight FemaleWeight 1 178 61 177 51 2 172 60 169 73 3 174 57 173 53 4 152 62 180 50 5 169 68 168 54 6 177 56 153 68 7 154 69 150 56 8 155 71 175 75 9 160 73 171 60 10 150 50 165 64 11 151 75 156 72 12 168 79 174 78 13 173 64 179 62 14 170 65 178 70 15 161 55 152 65 16 171 67 166 67 17 157 53 158 59 18 153 58 159 55 19 163 72 151 63 20 167 76 170 80
To find the row means of columns having Male in the column name on the above created data frame, add the following code to the above snippet −
MaleHeight<-sample(150:180,20)
MaleWeight<-sample(50:80,20)
FemaleHeight<-sample(150:180,20)
FemaleWeight<-sample(50:80,20)
df2<-data.frame(MaleHeight,MaleWeight,FemaleHeight,FemaleWeight)
df2%%mutate(Males=select(.,starts_with("Male")) %% rowMeans())Output
If you execute all the above given snippets as a single program, it generates the following Output −
MaleHeight MaleWeight FemaleHeight FemaleWeight Males 1 178 61 177 51 119.5 2 172 60 169 73 116.0 3 174 57 173 53 115.5 4 152 62 180 50 107.0 5 169 68 168 54 118.5 6 177 56 153 68 116.5 7 154 69 150 56 111.5 8 155 71 175 75 113.0 9 160 73 171 60 116.5 10 150 50 165 64 100.0 11 151 75 156 72 113.0 12 168 79 174 78 123.5 13 173 64 179 62 118.5 14 170 65 178 70 117.5 15 161 55 152 65 108.0 16 171 67 166 67 119.0 17 157 53 158 59 105.0 18 153 58 159 55 105.5 19 163 72 151 63 117.5 20 167 76 170 80 121.5
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