Code covered by the BSD License

# PIVMat 3.02

### Frederic Moisy (view profile)

27 Apr 2006 (Updated )

A PIV Post-processing and data analysis toolbox

bwfilterf (PIVMat Toolbox)
bwfilterf (PIVMat Toolbox)
 PIVMat Function Reference << Prev | Next >>
bwfilterf
Butterworth filter for a vector/scalar field

Description ```FF = bwfilterf(F,FSIZE,ORDER) applies a lowpass Butterworth filter to the vector/scalar field F with a cutoff size FSIZE (in grid units) and order ORDER. Dimensions of FSIZE and ORDER must match the dimension of the field F. If FSIZE and/or ORDER are scalar, the same cutoff and order is applied to each field of F. bwfilterf first Fourier-transforms the field(s), applies a low/high-pass transfer function and inverse Fourier transforms. Typical values for FSIZE are around 1-10, and typical values for ORDER are in the range 2-10 (positive for a low-pass filter, negative for a high-pass filter). Sharp filters (ie large values of FSIZE) may produce oscillations. FF = bwfilterf(F,FSIZE,ORDER,OPT), where OPT is a string that may contain one or several substrings: 'low', 'high': specifies a lowpass (by default) or highpass filter 'trunc': truncates the borders of width FSIZE, which are affected by the filtering. The X and Y dimensions of the fields must be even. If one of the dimension is odd, the last column/row is discarded. If no output argument, the result is displayed by showf. Note 1: A highpass filter of order ORDER is equivalent to a lowpass filter of order -ORDER. Note 2: If there are missing data in the field, it is better to first interpolate the data. See interpf. Example v = loadvec('*.vc7'); showf(bwfilterf(v,3,8)); See Also filterf, interpf, addnoisef, truncf, extractf. Published output in the Help browser showdemo bwfilterf ```
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