 |
BUILT-IN MATHEMATICA SYMBOL
SparseArray
SparseArray[{pos1->val1, pos2->val2, ...}]
yields a sparse array in which values 
appear at positions 
.
SparseArray[{pos1, pos2, ...}->{val1, val2, ...}]
yields the same sparse array.
SparseArray[list]
yields a sparse array version of list.
SparseArray[data, {d1, d2, ...}]
yields a sparse array representing a 
array.
SparseArray[data, dims, val]
yields a sparse array in which unspecified elements are taken to have value val.
Details
- By default, SparseArray takes unspecified elements to be
. - SparseArray[data, ...] is always converted to an optimized standard form with structure SparseArray[Automatic, dims, val, ...].
- Normal[SparseArray[...]] gives the ordinary array corresponding to a sparse array object.
- ArrayRules[SparseArray[...]] gives the list of rules
. - The elements in SparseArray need not be numeric.
- The position specifications
can contain patterns. - SparseArray[{{i_, i_}->1}, {d, d}] gives a d×d identity matrix.
- Rules of the form Band[...]->vals specify values on bands in the sparse array.
- With rules
the 
are evaluated separately for each set of indices that match 
. - SparseArray[list] requires that list be a full array, with all parts at a particular level being lists of the same length.
- The individual elements of a sparse array cannot themselves be lists.
- SparseArray[rules] yields a sparse array with dimensions exactly large enough to include elements whose positions have been explicitly specified.
- SparseArray[rules, Automatic, val] takes unspecified elements to have value val.
- List and matrix operations are typically set up to work as they do on Normal[SparseArray[...]].
- Functions with attribute Listable are automatically threaded over the individual elements of the ordinary arrays represented by SparseArray objects.
- Part extracts specified parts of the array represented by a SparseArray object, rather than parts of the SparseArray expression itself.
- Functions like Map are automatically applied to components in a SparseArray object.
- SparseArray is treated as a raw object by functions like AtomQ and for purposes of pattern matching.
- Dimensions gives the dimensions of a sparse array.
- The standard output format for a sparse array indicates the number of nondefault elements and the total dimensions.
New in 5 | Last modified in 6
