# Difference between revisions of "Windowfilter"

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===See Also=== | ===See Also=== | ||

− | [[line_filter]], [[box_filter]] | + | [[line_filter]], [[box_filter]], [[madc]] |

## Latest revision as of 10:48, 5 December 2019

## Contents

### Purpose

Spectral filtering.

### Synopsis

- xf = windowfilter(x,win,options);
- xf = windowfilter(x,win,'algorithm');

### Description

Rows of X are filtered using a windowed filtering.
**Note**: To allow robust statistics the filter is based on a moving window (or box), and is slow compared to other filter methods.

#### Inputs

**x**= data of class 'double' or 'dataset'.

- If 'dataset' it must x.type=='data' or 'image'.
- If 'double' it must be MxN.

**win**= an odd integer corresponding to the window width of the filter.

#### Optional Inputs

**algorithm**= an string which will be used as the options.algorithm input (only valid when options input is omitted)

#### Outputs

**xf**= Filtered spectra class 'dataset'.

### Options

options = a structure array with the following fields:

**display**: [ {'on'} | 'off' ], governs level of display,**algorithm**: [ {'mean'} | 'median' | 'max' | 'min' | 'despike' | 'meantrimmed' | 'mediantrimmed' ] governs filter method.

despike parameters

**tol**: { [] } if empty then despike uses the std(median(x))*within each window*to define the tolerance within the window. If tol>0 scalar, then tol defines the tolerance*for all the windows*. If tol<=0, then tol is estimated by the mean absolute deviation of madc(x.data(:)) and is the tolerance used for all the windows (see MADC).**dsthreshold**: [ {2} ] Threshold used for the 'despike' algorithm. In contrast to replacing all values with the meidan (e.g., for options.algorithm = 'median'), 'despike' replaces only values outside |x-median(x)|>options.dsthreshold*options.tol with the median. (see options.tol)**trbflag**: [ {'middle'} | 'bottom' | 'top' ] top-or-bottom flag. For trbflag = 'middle' the filter replaces values outside |x-median(x)|>dsthreshold*options.tol) with the median. For trbflag = 'bottom' the filter replaces values outside (x-median(x))>dsthreshold*options.tol with the median. For trbflag = 'top' the filter replaces values outside (median(x)-x)>dsthreshold*soptions.tol with the median.

ntrim parameters

**ntrim**: when algorithm = 'meantrimmed' or 'mediantrimmed', (ntrim) is the input (n) to the functions MEANTRIMMED or MEDIANTRIMED {default = 2}.