How to identify outliers and remove?

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pink flower
pink flower 2020-12-14
回答： Image Analyst 2020-12-14
Hello!
I have a .txt file with a lot of data and I need to identify and remove outliers. I already tried the command
rmoutliers
but it returns:
Undefined function or variable 'rmoutliers'.
Does anyone have any solution that can help me? I use MATLAB R2017a.
  1 个评论
Rik
Rik 2020-12-14
You will have to use a different function: that one was introduced in R2018b.
Have you tried Google? I alread see two links to file exchange submission in the sidebar (one and two). Have you looked at anything on the FEX and what functions those submissions use?

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回答（1 个）

Image Analyst
Image Analyst 2020-12-14
pink, you can try it yourself with movmedian(), introduced in R2016a. Try this demo I made especially for you.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 22;
fprintf('Beginning to run %s.m ...\n', mfilename);
% Create sample noisy data.
x = linspace(0, 4*pi, 1000);
y = sin(x) + 0.1 * rand(1, length(x));
% Get 20 random indexes where we can add noise.
noiseIndexes = sort(randperm(length(x), 20));
y(noiseIndexes) = y(noiseIndexes) + 0.75 + rand(1, length(noiseIndexes));
subplot(3, 1, 1);
plot(x, y, 'b-');
grid on;
title('Original Signal', 'FontSize', fontSize);
% Smooth the signal with a median filter.
ySmooth = movmedian(y, 9);
% Get the median absolute deviation everywhere.
madValues = abs(y - ySmooth);
subplot(3, 1, 2);
plot(x, madValues, 'b-');
grid on;
title('MAD Signal', 'FontSize', fontSize);
% Find the bad indexes where MAD > 3
outlierIndexes = madValues > 0.3; % You can adjust this.
hold on;
plot(x(outlierIndexes), madValues(outlierIndexes), 'ro', 'LineWidth', 2);
grid on;
% Repair the signal by replacing the outlier locations
% with the smoothed signal at those locations.
y(outlierIndexes) = ySmooth(outlierIndexes);
subplot(3, 1, 3);
plot(x, y, 'b-');
grid on;
title('Repaired Signal', 'FontSize', fontSize);
If that doesn't work, then attach your signal with the paper clip icon.

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