How to find X Value given Y value and show the point on a plot

I have an semilog plot below.

 %
x = 0:1:25;
y = exp(-0.03*x);
figure;
semilogy(x,y);
%

I want to let the program calculate the x value when y=0.5 and indicate this point (x,0.5) on the plot with dashed lines connecting to the two axes. How do I achieve this?

Answer 1

[KSSV]

x = 0:1:25;
y = exp(-0.03*x);
figure;
semilogy(x,y);
%
yi = 0.5 ;
xi = interp1(y,x,yi) ;

hold on

semilogy(xi,yi,'*r')

[Alessandro Amador]

is there a way to make it display the value of the point on the graph?

[Babu Sankhi]

I am also looking for the answer of this question .

In addition, How can I do it if Xi does not have unique value?

[Coryn Melissa LLamoza Carabali]

yes! looking for both questions above. Anybody that can help with this ;(

[Onu Student]

you can add annotations to plots text(x,y,txt)