applyFilter: Function for applying convolution kernel to a matrix or array

In spatialfil: Application of 2D Convolution Kernel Filters to Matrices or 3D Arrays

Description

This function applies the a convolution kernel based filter to a matrix or array object type.

Usage

applyFilter(x, kernel)

Arguments

x	An object of class matrix or array
kernel	A matrix containing the values chosen as convolution kernel

Details

The application of a convolution kernel over a 2D matrix dataset allows to apply functions as smoothing or edge detection. The aim of this function is to filter 2D matrices in order to help signal finding across (images-derived) data. It is also possible to filter 3D arrays considering them as slices of a series of images to be processed. Higher dimensions arrays are not allowed. The kernel parameter is a simple square matrix with an odd number of rows/columns, that can be pre-calculated by using the function convKernel. Not square matrices or matrices with even number of rows/columns will exit an error.

Value

An object with the same size of x containing data processed by convolution kernel

Examples

## Not run:
M <- array(runif(1000000), dim = c(100,100,100))
# smooth the array M
Mfil <- applyFilter(x = M, kernel = convKernel(sigma = 1.4, k = 'gaussian'))
image(M[,,50], col = grey(1:1000/1000))
image(Mfil[,,50], col = grey(1:1000/1000))

# now combining two filters in cascade
Mfil <- applyFilter(x = applyFilter(x = M, kernel = convKernel(k = 'sobel')),
                    kernel = convKernel(sigma = 1.4, k = 'gaussian'))
image(Mfil[,,50], col = grey(1:1000/1000))
## End(**Not run**)

Example output

Loading required package: abind
Loading required package: fields
Loading required package: spam
Loading required package: dotCall64
Loading required package: grid
Spam version 2.2-2 (2019-03-07) is loaded.
Type 'help( Spam)' or 'demo( spam)' for a short introduction 
and overview of this package.
Help for individual functions is also obtained by adding the
suffix '.spam' to the function name, e.g. 'help( chol.spam)'.

Attaching package: 'spam'

The following objects are masked from 'package:base':

    backsolve, forwardsolve

Loading required package: maps
See https://github.com/NCAR/Fields for
 an extensive vignette, other supplements and source code 

spatialfil documentation built on May 2, 2019, 8:53 a.m.