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Glacius

Builds on algebra

Linear algebra

Understand vectors, matrices, and the geometry behind data and its transformations.

Start with vector coordinates 54 lessons · 11 units
6−42
Explore dot products

Inside this subject

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01Vectors8 lessons
  1. 01
    Vector coordinates

    Interpret the entries of a vector in a named coordinate system.

  2. 02
    Vector addition

    Add two vectors of the same dimension.

  3. 03
    Scalar multiplication

    Scale each coordinate of a vector by a scalar.

  4. 04
    Vector differences

    Compute the displacement between two coordinate vectors.

  5. 05
    Linear combinations

    Construct a weighted sum of supplied vectors.

  6. 06
    Dot products

    Compute the dot product of two equal-length vectors.

  7. 07
    Euclidean length

    Compute the Euclidean length of a vector.

  8. 08
    Unit vectors

    Normalize a nonzero vector to unit length.

02Vector geometry5 lessons
  1. 01
    Euclidean distance

    Compute the Euclidean distance between two vectors.

  2. 02
    Orthogonal vectors

    Decide whether two vectors are orthogonal using their dot product.

  3. 03
    Cosine similarity

    Compute directional similarity for two nonzero vectors.

  4. 04
    Embedding similarity

    Interpret a supplied embedding ranking within its stated representation.

  5. 05
    L1 norm

    Compute the L1 norm of a vector.

03Matrices as operations6 lessons
  1. 01
    Matrix shape

    Identify the row and column dimensions of a matrix.

  2. 02
    Matrix entries

    Retrieve a matrix entry using its row and column indices.

  3. 03
    Matrix addition

    Add matrices of equal shape.

  4. 04
    Matrix scaling

    Multiply each matrix entry by a scalar.

  5. 05
    Matrix-vector products

    Compute a matrix-vector product from row dot products.

  6. 06
    Column combinations

    Express a matrix-vector product as a combination of its columns.

04Matrix products4 lessons
  1. 01
    Matrix products

    Compute the entries of a compatible matrix product.

  2. 02
    Matrix transpose

    Transpose a rectangular matrix.

  3. 03
    Diagonal matrices

    Interpret the coordinate scaling performed by a diagonal matrix.

  4. 04
    Outer products

    Construct an outer product from two vectors.

05Eliminating variables6 lessons
  1. 01
    Systems as matrices

    Encode a finite linear system as Ax=b.

  2. 02
    Row operations

    Apply one solution-preserving elementary row operation.

  3. 03
    Gaussian elimination

    Eliminate a variable using elementary row operations.

  4. 04
    Pivots

    Identify pivot positions in row-echelon form.

  5. 05
    Back substitution

    Solve a triangular system by back substitution.

  6. 06
    Reduced echelon form

    Reduce an echelon matrix to reduced row-echelon form.

06Solutions and inverses3 lessons
  1. 01
    Inconsistent systems

    Detect a contradictory row in an augmented system.

  2. 02
    Free variables

    Parameterize the free variables of a consistent reduced system.

  3. 03
    Unique solutions

    Determine whether a consistent system has a unique solution.

07Span and basis5 lessons
  1. 01
    Span

    Decide whether a vector lies in the span of supplied vectors.

  2. 02
    Subspaces

    Check the defining closure conditions for a candidate real subspace.

  3. 03
    Linear independence

    Test whether a supplied vector list is linearly independent.

  4. 04
    Bases

    Verify a basis for a specified finite-dimensional subspace.

  5. 05
    Dimension

    Determine subspace dimension from a basis.

08Matrix subspaces2 lessons
  1. 01
    Column space

    Find a basis for the column space of a matrix.

  2. 02
    Matrix rank

    Determine matrix rank from its pivots.

09Linear maps3 lessons
  1. 01
    Linearity

    Check additivity and homogeneity for a candidate map.

  2. 02
    Composing maps

    Represent a composition of linear maps as an ordered matrix product.

  3. 03
    Affine maps

    Separate the linear part from the translation in an affine map.

10Projections and least squares6 lessons
  1. 01
    Projection onto a line

    Compute the orthogonal projection onto a nonzero vector's span.

  2. 02
    Orthonormal bases

    Verify that a supplied basis is orthonormal.

  3. 03
    Projection onto a subspace

    Project a vector using a supplied orthonormal basis.

  4. 04
    Least-squares geometry

    Identify the closest attainable output in an inconsistent linear system.

  5. 05
    QR factorization

    Use supplied reduced QR factors to solve a full-column-rank least-squares problem.

  6. 06
    Normal equations

    Form the normal equations for a linear least-squares problem.

11Low-rank approximation6 lessons
  1. 01
    Singular value decomposition

    Interpret the three transformations in a supplied SVD.

  2. 02
    Singular values

    Infer rank from the nonzero singular values of a matrix.

  3. 03
    Truncated SVD

    Construct a rank-k approximation from supplied singular components.

  4. 04
    Frobenius norm

    Compute a matrix's Frobenius norm.

  5. 05
    Approximation error

    Compute truncated-SVD Frobenius error from discarded singular values.

  6. 06
    Condition numbers

    Interpret the ratio of largest to smallest nonzero singular values for a full-rank square system.