Finding basis of a column space/row space

In summary, there are two types of operations that can be used to reduce a matrix: row operations and column operations. However, these operations cannot be used interchangeably when trying to find the column space or row space of a matrix. Taking the transpose of a matrix does not change this fact. Additionally, the column space and row space may have different dimensions, unless the matrix is square. In that case, they will have the same dimension but are not necessarily the same spaces.
  • #1
ashina14
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I was wondering whether we can use row as well as column operations to reduce a matrix to find column space? Or do we only have to perform row operations to reduce matrix in case of row space and column operations to find column space?
 
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  • #2
You could, of course, take the transpose of a matrix, so that "columns" become rows and vice versa, but the "column space" of a matrix (the space spanned by its columns as vectors) is NOT, in general, the same as the "row space" of a matrix (the space spanned by it rows). If the matrix is not square, the will have completely different dimensions. If the matrix is square, the row space and column space will have the same dimension and so be "isomorphic" but not, in general, the "same" spaces.
 

1. What is the column space and row space of a matrix?

The column space of a matrix is the space spanned by the columns of the matrix. It represents all possible linear combinations of the columns. The row space, on the other hand, is the space spanned by the rows of the matrix. It represents all possible linear combinations of the rows.

2. Why is finding the basis of a column space/row space important?

The basis of a column space/row space provides a minimal set of vectors that span the space. This can be useful in solving systems of linear equations or in finding solutions to other mathematical problems. Additionally, the basis can help in understanding the structure and properties of the matrix.

3. How do you find the basis of a column space/row space?

To find the basis of a column space/row space, we first reduce the matrix to its row-echelon or reduced row-echelon form using elementary row operations. Then, we select the pivot columns/rows as the basis vectors. If there are any non-pivot columns/rows, we add them to the basis. The resulting vectors will form the basis for the column space/row space.

4. Can a column space and row space have different bases?

Yes, it is possible for a column space and row space to have different bases. This can happen when the matrix is not square, and therefore, the dimensions of the column space and row space are different. In this case, the basis vectors for the column space and row space will also be different.

5. How does finding the basis of a column space/row space relate to matrix rank?

The rank of a matrix is equal to the number of linearly independent columns/rows, which is also equal to the number of elements in the basis of the column space/row space. Therefore, finding the basis of a column space/row space can help determine the rank of the matrix, which is an important property in solving systems of linear equations and other mathematical problems.

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