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Find the column name of least value in each row of an R dataframe.
To find the column name that has the least value for each row in an R data frame, we can use colnames function along with apply function.
For Example, if we have a data frame called df then we can find column name that has the least value for each row by using the command mentioned below −
df$Least_Column<-colnames(df)[apply(df,1,which.min)]
Example 1
Following snippet creates a sample data frame −
x1<-rpois(20,10) x2<-rpois(20,10) x3<-rpois(20,10) x4<-rpois(20,10) df1<-data.frame(x1,x2,x3,x4) df1
The following dataframe is created
x1 x2 x3 x4 1 6 12 9 8 2 15 16 9 9 3 8 7 11 10 4 13 8 8 9 5 14 10 15 15 6 5 10 4 10 7 10 13 5 9 8 7 7 9 12 9 9 14 11 8 10 6 9 6 10 11 12 12 10 12 12 8 4 12 9 13 8 9 15 14 14 14 9 8 6 15 10 15 12 12 16 13 9 8 13 17 11 15 7 11 18 11 13 9 7 19 14 8 12 6 20 7 6 13 10
To find the column name that has the least value for each row in df1 on the above created data frame, add the following code to the above snippet −
x1<-rpois(20,10) x2<-rpois(20,10) x3<-rpois(20,10) x4<-rpois(20,10) df1<-data.frame(x1,x2,x3,x4) df1$Smallest_Col<-colnames(df1)[apply(df1,1,which.min)] df1
Output
If you execute all the above given snippets as a single program, it generates the following Output −
x1 x2 x3 x4 Smallest_Col 1 6 12 9 8 x1 2 15 16 9 9 x3 3 8 7 11 10 x2 4 13 8 8 9 x2 5 14 10 15 15 x2 6 5 10 4 10 x3 7 10 13 5 9 x3 8 7 7 9 12 x1 9 9 14 11 8 x4 10 6 9 6 10 x1 11 12 12 10 12 x3 12 8 4 12 9 x2 13 8 9 15 14 x1 14 14 9 8 6 x4 15 10 15 12 12 x1 16 13 9 8 13 x3 17 11 15 7 11 x3 18 11 13 9 7 x4 19 14 8 12 6 x4 20 7 6 13 10 x2
Example 2
Following snippet creates a sample data frame −
y1<-round(rnorm(20),2) y2<-round(rnorm(20),2) y3<-round(rnorm(20),2) df2<-data.frame(y1,y2,y3) df2
The following dataframe is created
y1 y2 y3 1 -0.33 0.19 -0.18 2 -1.41 -0.42 -0.06 3 -0.48 -0.62 -0.51 4 -0.27 0.68 0.38 5 1.00 1.04 1.31 6 -0.29 0.04 -1.23 7 0.65 -1.47 -1.11 8 0.33 0.14 0.80 9 1.29 0.20 1.14 10 -0.26 0.10 0.64 11 0.42 -0.17 0.64 12 -0.31 1.53 -0.41 13 0.21 -0.87 -1.03 14 0.85 1.82 -1.35 15 0.80 0.89 0.45 16 0.65 1.08 0.08 17 -0.05 -1.16 0.35 18 -0.91 -0.19 -0.93 19 0.14 -1.30 -0.91 20 -0.03 2.02 1.41
To find the column name that has the least value for each row in df2 on the above created data frame, add the following code to the above snippet −
y1<-round(rnorm(20),2) y2<-round(rnorm(20),2) y3<-round(rnorm(20),2) df2<-data.frame(y1,y2,y3) df2$Smallest_Col<-colnames(df2)[apply(df2,1,which.min)] df2
Output
If you execute all the above given snippets as a single program, it generates the following Output −
y1 y2 y3 Smallest_Col 1 -0.33 0.19 -0.18 y1 2 -1.41 -0.42 -0.06 y1 3 -0.48 -0.62 -0.51 y2 4 -0.27 0.68 0.38 y1 5 1.00 1.04 1.31 y1 6 -0.29 0.04 -1.23 y3 7 0.65 -1.47 -1.11 y2 8 0.33 0.14 0.80 y2 9 1.29 0.20 1.14 y2 10 -0.26 0.10 0.64 y1 11 0.42 -0.17 0.64 y2 12 -0.31 1.53 -0.41 y3 13 0.21 -0.87 -1.03 y3 14 0.85 1.82 -1.35 y3 15 0.80 0.89 0.45 y3 16 0.65 1.08 0.08 y3 17 -0.05 -1.16 0.35 y2 18 -0.91 -0.19 -0.93 y3 19 0.14 -1.30 -0.91 y2 20 -0.03 2.02 1.41 y1
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