We modify the R matrix by using the various indexing techniques along with the assignment operator. When using this technique, the result is a vector formed by stacking the columns of the matrix one after another. We can index the R matrix with a single vector.
We can also use these indexing techniques in combination with one another as well. When using logical vectors for indexing, R recycles the vector, if the length of the indexing vector is not equal to the matrix’s dimensions.Ĭode: > mat2 #the row vector is recycled to 3 elements.įor matrices with named rows and columns, we can use the row and column names to access elements of the R matrix.Ĭode: > named_matrix
This excludes the row/columns corresponding to FALSE and includes the one corresponding to TRUE.Ĭode: > mat2 We can use logical vectors of the same lengths as the matrix’s dimensions to specify the rows and columns needed. We can use the drop=FALSE argument to avoid this behavior.Ĭode: > mat2 #first row second column of mat2Ĭode: > mat2 #first row and second and third column are excluded If we select a single row or column this way, the result is a vector and not a matrix. We can also use negative integers to exclude rows or columns. If we leave the row or column field blank inside the square brackets, R selects all the rows/columns. We can specify the needed row and column numbers in vectors and use them to index a matrix. We can use the vector indexing techniques to index a matrix, similar to vector indexing. We can access the elements of a matrix named mat using square brackets as mat, where row and col are the vectors. How to access individual components of the R matrix? For example:Ĭode: > rownames(mat1) colnames(mat1) mat1 We can also name the rows and columns of an R matrix after its creation by using the rownames() or colnames() functions. For example:Ĭode: > rnames cnames named_matrix named_matrix It is possible to name the rows and columns of the matrix during creation with the dimnames argument of the matrix() function. How to name the rows and columns of an R matrix? We can also create an R matrix by changing a vector’s dimensions using the dim() function. For example:Ĭode: > mat3.data1 mat3.data2 mat3.data3 mat3 mat3 Using rbind() or cbind() FunctionĪnother way of creating an R matrix is to combine vectors as rows or columns using the rbind() or cbind() functions. Note- Notice how without the byrow=TRUE argument, the matrix mat2 is column-wise. R calculated the other based on the length of the data. Note – It is not necessary to specify both nrow and ncol. Here is an example of creating a matrix with the matrix() function: dimnames – takes two character arrays as input for row names and column names.ncol – defines the number of columns in the R matrix.nrow – defines the number of rows in the R matrix.By setting byrow as TRUE, we can arrange the data row-wise in the matrix. data – data contains the elements in the R matrix.The arguments in the matrix function are the following: We can create matrics using the matrix() function.
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