Extracting values from matrix by row names
A column subset matrix can be extracted from the original matrix using a filter for the selected column names. Since a matrix’s elements are accessed in a dual index format, particular row selection can be carried out.
Syntax:
matrix[ , vec ]
Where, vec contains the column names to be fetched
All the rows for the selected columns are retrieved from the data frame. The order of the rows and columns remains unmodified. The rows and column names remain unchanged after extraction. The result returned is a subset of the original matrix. The column names to be chosen should be a proper subset of the original row names pertaining to the matrix.
Example:
R
# declaring matrix mat <- matrix ( letters [1:12], ncol = 3) # naming columns colnames (mat) <- c ( "C1" , "C2" , "C3" ) # naming rows rownames (mat) <- c ( "R1" , "R2" , "R3" , "R4" ) print ( "Original Matrix" ) print (mat) # extracting rows col_vec <- c ( "C1" , "C3" ) col_mat <- mat[,col_vec] print ( "Modified Matrix" ) print (col_mat) |
Output
[1] "Original Matrix" C1 C2 C3 R1 "a" "e" "i" R2 "b" "f" "j" R3 "c" "g" "k" R4 "d" "h" "l" [1] "Modified Matrix" C1 C3 R1 "a" "i" R2 "b" "j" R3 "c" "k" R4 "d" "l"
Extract Values from Matrix by Column and Row Names in R
In this article, we will discuss how to extract values from the matrix by column and row names in R Programming Language.
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