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# STFILTER

STFILTER = “filter” - A special type of `ST` that represents a polynomial filter.

## Notes

In standard eigenvalue problems, when the eigenvalues of interest are interior to the spectrum and we want to avoid the high cost associated with the matrix factorization of the shift-and-invert spectral transformation, an alternative is to build a high-order polynomial such that \(p(A)\) enhances the wanted eigenvalues and filters out the unwanted ones.

The definition of the filter is done with functions such as `STFilterSetDegree()`, `STFilterSetInterval()` or `STFilterSetType()`.

## See Also

ST: Spectral Transformation, `ST`, `STType`, `STSetType()`, `STSetMatrices()`, `STFilterSetDegree()`, `STFilterSetInterval()`, `STFilterSetType()`

## Level

beginner

## Location

src/sys/classes/st/impls/filter/filter.c

Index of all ST routines Table of Contents for all manual pages Index of all manual pages