Peak Width at Half Height
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Laiba Qadeer
am 10 Mär. 2020
Kommentiert: Rufus Adjetey
am 13 Nov. 2020
I started using MATLAB only a few days ago. And I have trouble finding the width of peak. I have two subplots, both of which represent one peak from the data only. I want to know the width of peak at half distance. I also want the line representing width to be displayed on the plot. Please tell me how this can be done.
I searched the internet for help but could not get the desired result.
Here is my code for both graphs:
subplot(2,1,1)
plot(Hwave,Hintense,'.'),title('Original data'),xlabel('Wavelength'),ylabel('Intensity')
axis tight, grid
subplot(2,1,2)
plot(Hwaveinter,Hreal,'.'),title('Eight Times Interpolated Data'),xlabel('Wavelength'),ylabel('Intensity')
axis tight, grid
Thanks
3 Kommentare
Akzeptierte Antwort
Image Analyst
am 10 Mär. 2020
Bearbeitet: Image Analyst
am 10 Mär. 2020
See this demo:
% Initialization steps.
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 = 24;
% Make Gaussian https://en.wikipedia.org/wiki/Gaussian_function
x = linspace(0, 100, 1024);
amp = 50;
mu = 35;
sigma = 20;
y = amp * exp(-(x - mu).^2 / (2 * sigma^2));
hFig = figure;
plot(x, y, 'b-', 'LineWidth', 2);
grid on;
xlabel('x', 'FontSize', fontSize);
ylabel('y', 'FontSize', fontSize);
hFig.WindowState = 'maximized';
% Find the half height - midway between min and max y values.
halfHeight = (min(y) + max(y)) / 2;
hold on;
yline(halfHeight, 'Color', 'g', 'LineWidth', 2);
% Find left edge
index1 = find(y >= halfHeight, 1, 'first');
x1 = x(index1)
line([x1, x1], [0, y(index1)], 'Color', 'r', 'LineWidth', 2);
text(x1+1, 5, sprintf('x1 = %.2f', x1), 'FontSize', fontSize, 'Color', 'r');
% Find right edge
index2 = find(y >= halfHeight, 1, 'last');
x2 = x(index2)
line([x2, x2], [0, y(index2)], 'Color', 'r', 'LineWidth', 2);
text(x2+1, 5, sprintf('x2 = %.2f', x2), 'FontSize', fontSize, 'Color', 'r');
% Compute the full width, half max.
fwhm = x2 - x1
text(mu, halfHeight+2, sprintf('width = %.2f', fwhm), 'FontSize', fontSize, 'Color', 'r', 'HorizontalAlignment', 'center');
caption = sprintf('Full Width, Half Max = %.2f', x2 - x1);
title(caption, 'FontSize', fontSize);
Adapt code as needed for your variable names.
12 Kommentare
Image Analyst
am 12 Nov. 2020
You data is discrete - it's quantized. There are no elements that are exactly 0.6 for y. So it picks the closest element above that. If you want to interpolate with interp1() or polyval(), you're certainly welcome to do that.
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