In mathematics, a **bidiagonal matrix** is a matrix with non-zero entries along the main diagonal and *either* the diagonal above or the diagonal below. This means there are exactly two non zero diagonals in the matrix.

When the diagonal above the main diagonal has the non-zero entries the matrix is **upper bidiagonal**. When the diagonal below the main diagonal has the non-zero entries the matrix is **lower bidiagonal**.

For example, the following matrix is **upper bidiagonal**:

and the following matrix is **lower bidiagonal**:

Read more about Bidiagonal Matrix: Usage

### Famous quotes containing the word matrix:

“As all historians know, the past is a great darkness, and filled with echoes. Voices may reach us from it; but what they say to us is imbued with the obscurity of the *matrix* out of which they come; and try as we may, we cannot always decipher them precisely in the clearer light of our day.”

—Margaret Atwood (b. 1939)