Band

Band[{i,j}]

represents the sequence of positions on the diagonal band that starts with {i,j} in a sparse array.

Band[{imin,jmin,…},{imax,jmax,…}]

represents the positions between {imin,jmin,…} and {imax,jmax,…}.

Band[{imin,jmin,…},{imax,jmax,…},{di,dj,…}]

represents positions starting with {imin,jmin,…} and then moving with step {di,dj,…}.

Details

  • Band[pos]->v represents values v that repeat along the diagonal band starting at pos.
  • Band[pos]->{v1,v2,…} represents a sequence of values vn along the diagonal band starting at pos.
  • With an array a of the same rank as the whole sparse array, Band[start]->a by default inserts a at the position specified by start.
  • With arrays an of the same rank as the whole sparse array, Band[pos]->{a1,a2,…} represents a sequence of non-overlapping subarrays.
  • Band[start] is effectively equivalent to Band[start,{-1,-1,…}].
  • For scalar values, Band[start,end] is equivalent to Band[start,end,{1,1,…}].
  • Band[start,end,step] stops when any coordinate first exceeds its value in end.
  • Band[start,end]->{v1,v2,…} takes the values vn to repeat cyclically until end is reached.
  • Band[start,Automatic,step]->a continues until the edge of the array is reached.
  • Band[start,Automatic,step]->{v1,v2,…} continues until the vi are exhausted.

Examples

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Basic Examples  (1)

Create a band diagonal matrix:

Convert to normal lists:

Scope  (11)

Mix Band with other SparseArray element specifications:

Give explicit values to fill in on the band:

Repeat the values cyclically:

Start the band at any position in the matrix:

Specify any start and end locations:

Step by 2 between elements on the band:

Any step can be used:

Automatically continue the band to the edge of the array:

Specify a band that is part of a row:

Specify an anti-diagonal matrix:

Insert a submatrix beginning at position 3, 3:

Cyclically repeat the submatrix:

Alternate the submatrix with a single element:

Generalizations & Extensions  (2)

Band works in sparse arrays of any rank:

Fill in a plane of values into a 3D sparse array:

Applications  (2)

Make a tridiagonal matrix:

Build a tridiagonal linear system:

Properties & Relations  (2)

Band works in SparseArray; use Normal to convert to normal lists:

The simplest case of Band is equivalent to DiagonalMatrix:

Wolfram Research (2007), Band, Wolfram Language function, https://reference.wolfram.com/language/ref/Band.html.

Text

Wolfram Research (2007), Band, Wolfram Language function, https://reference.wolfram.com/language/ref/Band.html.

CMS

Wolfram Language. 2007. "Band." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Band.html.

APA

Wolfram Language. (2007). Band. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Band.html

BibTeX

@misc{reference.wolfram_2024_band, author="Wolfram Research", title="{Band}", year="2007", howpublished="\url{https://reference.wolfram.com/language/ref/Band.html}", note=[Accessed: 22-December-2024 ]}

BibLaTeX

@online{reference.wolfram_2024_band, organization={Wolfram Research}, title={Band}, year={2007}, url={https://reference.wolfram.com/language/ref/Band.html}, note=[Accessed: 22-December-2024 ]}