Find the intersection point between 2 curves

조회 수: 2 (최근 30일)
Antonio Sepe
Antonio Sepe 2019년 5월 6일
댓글: Antonio Sepe 2019년 5월 7일
Hi there!
I'm a new matlab user so I don't know all its features.
I'm having trouble in finding the intersection point between two curves (I_moon and Moon_ref). Can you help me?
This is my code:
%------------------------------------------------------------------------%
%------------------------------------------------------------------------%
%-----------------Average radiance emitted and reflected-----------------%
%------------------------------------------------------------------------%
%------------------------------------------------------------------------%
%Target: Moon;
%Atmosphere and surface: no atmosphere;
%Surface temperature: 130 K;
%Albedo: 0.136;
%Wavelength range: 0-50 μm;
%Data from: nasa.gov
clear all;
close all;
clear global;
clc
%--------------------------------Costants--------------------------------%
c=2.998*10^8; % speed of light in vacuum
h=6.6261*10.^-34; % Planck constant
k=1.38*10.^-23; % Boltzmann constant
sigma=5.67*(10^-8); %Stephen-Boltzmann constant
L=(0.0:0.01:50); %wavelength (μm)
T=130; %Moon average temperature (K)
albedo=0.136; %Moon albedo (ad)
d=1; %Sun-Moon distance (AU)
R=1737.1; %Moon average radius (km)
r=4.66e-3; %Sun radius (AU)
T_sun=5777; %Sun average temperature (K)
Fs=1366; %Solar constant at 1 AU (W/m^2)
%----------------------------Radiance emitted----------------------------%
I_sun=3.742./((L.^5).*(exp(1.439e4./(L.*5777))-1));
I_moon=3.742./((L.^5).*(exp(1.439e4./(L.*130))-1));
%---------------------------Radiance reflected---------------------------%
Moon_ref=albedo*((r^2)/(1^2))*I_sun;
%------------------------------Absorptance-------------------------------%
F=Fs*(1./(d.^2)); %Solar constants for Moon=1366 (W/(m^2))
Rad_intercepted=F.*pi.*((R.*(10^3)).^2); %Solar radiation intercepted by Moon=1.295 (W)
Rad_absorbed=F.*(1-albedo).*pi.*((R.*(10^3)).^2); %Radiation absorbed: Moon=1.1188e+16 (W)
Abs=Rad_absorbed./Rad_intercepted; %Absorptance values for: Moon=0.864
%---------------------------Total radiance-------------------------------%
ToT_moon=Moon_ref+(Abs*I_moon);
figure4 = figure;
axes1 = axes('Parent',figure4);
hold(axes1,'on');
ylabel({'Radiance'});
xlabel({'wavelength (μm)'});
title({'Moon','(130K)'});
xlim(axes1,[1 20]);
ylim(axes1,[1e-30 1]);
set(axes1,'YMinorTick','on','YScale','log');
plot(L,I_moon,'Color',[0 0 1]);
hold on
plot(L,Moon_ref,'Color',[1 0 0]);
plot(L,ToT_moon,'Color',[0 0 0]);
hold off;
legend({'Emitted','Reflected','Total'},'Location','southeast');

답변 (1개)

Stephan
Stephan 2019년 5월 6일
create a function handle depending from wave length, that subtracts both from each other. this is the objective function for using fzero function. As result you get the interception wave length.
  댓글 수: 1
Antonio Sepe
Antonio Sepe 2019년 5월 7일
Hi! Thanks for the answer.
I tried to use fzero funcion but it didn't work.
I solved the problem by using polyxpoly, in this way (consider data in my question):
[xint,yint] = polyxpoly(L,I_moon,L,Moon_ref);
figure4 = figure;
axes1 = axes('Parent',figure4);
hold(axes1,'on');
ylabel({'Radiance'});
xlabel({'wavelength (μm)'});
title({'Moon','(130K)'});
xlim(axes1,[1 20]);
ylim(axes1,[1e-30 1]);
set(axes1,'YMinorTick','on','YScale','log');
plot(L,I_moon,'Color',[0 0 1]);
hold on
plot(L,Moon_ref,'Color',[1 0 0]);
plot(L,ToT_moon,'Color',[0 0 0]);
mapshow(xint,yint,'Displaytype','point','Marker','o');
legend({'Emitted','Reflected','Total','λ equiv.'},'Location','southeast');
hold off
Thx anyway :)

댓글을 달려면 로그인하십시오.

카테고리

Help CenterFile Exchange에서 Weather and Atmospheric Science에 대해 자세히 알아보기

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by