MedianFilter
Advanced Analysis Library Only
AnalysisLibErrType MedianFilter (double xArray[], ssize_t numberOfXAndYElements, ssize_t leftRank, ssize_t rightRank, double y[]);
Purpose
Filters the input array using a median filter. MedianFilter can perform the operation in place; that is, the input and output arrays can be the same. MedianFilter filters the input array xArray using the following equation:
Yi = Median(Ji) for i = 0, 1, 2, ..., n – 1
Where Y represents the output sequence of filtered data y, n is the number of elements in xArray, Ji is a subset of the input xArray centered about the ith element of xArray, and the indexed elements outside the range of xArray equal zero. The following equation describes Ji.
Ji = {xi–rl, xi–rl+1, ..., xi–1, xi, xi+1, ..., xi+rr–1, xi+rr},
Where rl is the left rank and rr is the right rank.
The following illustration shows the computation of yi.
Example Code
/* Generate a random signal and filter it using a median filter. */
double x[256], y[256];
ssize_t n, leftrank, rightrank;
int status;
n = 256;
leftrank = 2;
rightrank = 3;
Uniform (n, 17, x);
status = MedianFilter(x, n, leftrank, rightrank, y);
Parameters
| Input | ||
| Name | Type | Description |
| xArray | double [] | Array containing the raw data to filter. |
| numberOfXAndYElements | ssize_t | Number of elements in both the input and output array. |
| leftRank | ssize_t | Number of elements used to compute the median filter to the left side. leftRank must be greater than or equal to 0. |
| rightRank | ssize_t | Number of elements used to compute the median filter to the right side. rightRank must be less than leftRank. If rightRank is less than 0, rightRank is equal to leftRank. |
| Output | ||
| Name | Type | Description |
| y | double [] | Filtered data. |
Return Value
| Name | Type | Description |
| status | AnalysisLibErrType | A value that specifies the type of error that occurred. Refer to analysis.h for definitions of these constants. |
Additional Information
Library: Advanced Analysis Library
Include file: analysis.h
LabWindows/CVI compatibility: LabWindows/CVI 2012 and later