Plotting a non-linear graph in Matlab

3 次查看（过去 30 天）
Rihab el-Wali
Rihab el-Wali 2016-10-15
评论： Rihab el-Wali 2016-10-16
Hi guys,
I have this equation f(g)=1+cos(g)*cosh(g)-a*g*(cos(g)*sinh(g)-sin(g)*cosh(g))=0. I am trying to plot it for (a,g).
I have the initial condition that when a=0 then g=1.8751.
I am not sure how to code it as an equation with two unknowns and two initial values ??
My suggestion would be to plot the graph by using the solve function by using a=a+da (where da is small increment of a) and using the previous value of g as an initial value to find g for the new value of a.
Regards, Rihab
  3 个评论
显示 1更早的评论
Rihab el-Wali
Rihab el-Wali 2016-10-15
@Muhammad Usman Saleem I did mean to put two equal signs because the function is equal to zero. I want to plot (a,g) when f(g)=0.
Muhammad Usman Saleem
Muhammad Usman Saleem 2016-10-15
good night, tomorrow will guide u in this regards

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Walter Roberson
Walter Roberson 2016-10-16
a = linspace(-4, 2); %the interesting part of the graph
g = zeros(size(a));
oldguess = 1.8751;
for K = 1 : length(a)
fa = @(g) 1+cos(g)*cosh(g)-a(K)*g*(cos(g)*sinh(g)-sin(g)*cosh(g));
this_g = fzero(fa, oldguess);
g(K) = this_g;
oldguess = this_g;
end
plot(a, g)
However, there are many solutions. You will, for example, get a different plot if you start with oldguess = 50
  1 个评论
Rihab el-Wali
Rihab el-Wali 2016-10-16
That works! However, what if I want to plot for a larger range of a? When I change the vector size from [-4,2] to [0,100] the plot seems to look different.

请先登录，再进行评论。

更多回答（1 个）

Star Strider
Star Strider 2016-10-15
编辑：Star Strider 2016-10-15
When in doubt, plot first:
[A,G] = meshgrid(-0.5:0.01:0.5, -20:0.1:20);
fga = @(a,g) 1+cos(g).*cosh(g)-a.*g.*(cos(g).*sinh(g)-sin(g).*cosh(g))
F = fga(A,G);
figure(1)
meshc(A, G, F)
grid on
There appear to be a possibly infinite number of solutions. Which one do you want?

类别

在 Help Center 和 File Exchange 中查找有关 2-D and 3-D Plots 的更多信息

标签

Community Treasure Hunt

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

Start Hunting!

Translated by