How can I extract the width of the following graph.

4 次查看（过去 30 天）

显示更早的评论

Vahram Voskerchyan 2020-11-22

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/657608-how-can-i-extract-the-width-of-the-following-graph

回答： Mathieu NOE 2020-11-24

采纳的回答： Mathieu NOE

matlab_analysis_farfield.mat

在 MATLAB Online 中打开

I have made a farfield profile from the Phased Array and want to find how the width of the beam changes with the reduction of the number of emitting elements. I extract this data to matlab. And find the HWFM but when doing so I only get the same width for all the elements. The width doesn't change with the number of elements. But in my simulations the width is changing. This is the code that use for extracting the width. I only need the width of the main lobe of this plot. Which is the part of the highest intensity.

clear;
load('matlab_analysis_farfield.mat');
E_intensity = abs(E2);
 % Find the half max value.
halfMax = (min(E2) + max(E2)) / 2;
% Find where the data first drops below half the max.
index1 = find(E2 >= halfMax, 1, 'first');
% Find where the data last rises above half the max.
index2 = find(E2 >= halfMax, 1, 'last');
fwhm = index2-index1 + 1; % FWHM in indexes.
% OR, if you have an x vector
fwhmx = E2(index2) - E2(index1);
%I have found this code in the forum.
%to do check this if this works.
peakHeight = max(E2);
x1 = min(E2);
x2 = find(E2 <= peakHeight, 1, 'last');
theWidth = x2-x1; 

8 个评论
显示 6更早的评论隐藏 6更早的评论

Vahram Voskerchyan 2020-11-24

Thank you very much. I will adapt it.

Mathieu NOE 2020-11-24

you're welcome

may I ask you to accept my answer ?

I put it in the answer again so you can accept it

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Mathieu NOE 2020-11-24

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/657608-how-can-i-extract-the-width-of-the-following-graph#answer_554683

在 MATLAB Online 中打开

hello

this piece of code will give you the angle . Demo based on a half sinus wave.

you can easily apply it to your case

x= linspace(0,pi,100);
y = sin(x);
minus3dBpoint = 1/sqrt(2);      % -3 dB
z = abs(y-minus3dBpoint);
[p,loc] = findpeaks(-z);
plot(x,y,'b',x(loc),y(loc),'+r');
% angle = half of difference between the 2 elements of x(loc)
angle = diff(x(loc))/2