Dear all, how to select the values for k and f, of savitzky-golay filter?
MATLAB: Dear all, how to select the values for k and f, of savitzky-golay filter
signalSignal Processing Toolbox
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Do you have the Signal Processing Toolbox? If so, you could use the median filter. If you want to replace spikes with the median value around them, then compute the median and subtract it from the original and take the absolute value. Then replace those elements with a high value with the median.
medianSignal = medfilt1(signal, 7);diffSignal = abs(signal - medianSignal);spikes = diffSignal > 100; % Whatever...
% Replace
fixedSignal = signal; % Initialize
fixedSignal(spikes) = medianSignal(spikes);Or you can use the Savitzky-Golay filter, sgolayfilt(). A demo is attached.
If this is not right for you, then post your data - both a picture and the actual data in a txt or .mat file.
It's just 3 lines. Just mask the original image:
binaryImage = grayImage > 150;maskedImage = zeros(size(grayImage)); % Initialize.
maskedImage(binaryImage) = grayImage(binaryImage);See the full demo below:
% Demo by ImageAnalyst
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables.
workspace; % Make sure the workspace panel is showing.
fontSize = 14;% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');baseFileName = 'coins.png';% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);% Check if file exists.
if ~exist(fullFileName, 'file') % File doesn't exist -- didn't find it there. Check the search path for it.
fullFileName = baseFileName; % No path this time.
if ~exist(fullFileName, 'file') % Still didn't find it. Alert user.
errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName); uiwait(warndlg(errorMessage)); return; endendgrayImage = imread(fullFileName);% Get the dimensions of the image.
% numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(grayImage);% Display the original gray scale image.
subplot(2, 2, 1);imshow(grayImage, []);title('Original Grayscale Image', 'FontSize', fontSize);% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);% Give a name to the title bar.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') % Let's compute and display the histogram.
[pixelCount grayLevels] = imhist(grayImage);subplot(2, 2, 2); bar(pixelCount);grid on;title('Histogram of original image', 'FontSize', fontSize);xlim([0 grayLevels(end)]); % Scale x axis manually.
yl = ylim();line([150 150], [0 yl(2)], 'Color', 'r');% Threshold at 150
binaryImage = grayImage > 150;% Display the original gray scale image.subplot(2, 2, 3);imshow(binaryImage, []);title('Binary Image', 'FontSize', fontSize);% Mask the image
maskedImage = zeros(size(grayImage)); % Initialize.% Assign values from grayImage that are > 150.
maskedImage(binaryImage) = grayImage(binaryImage);% Display the original gray scale image.subplot(2, 2, 4);imshow(maskedImage, []);title('Masked Image', 'FontSize', fontSize);
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