MATLAB: How to find value of Y if i know X value from grap

plot marker find y data

i search on matlab searching question but not found it. I have a graph with a curve. I want to know the Y value from my graph example X = 10 to 11, till 10 to 11 in y axis i have to mark. how to find Y?
i also seen some example like this, i can find for one x value one y value, but continues x data how to mark in cureve
%example having only one x data X = 1:0.1:20;
Y = sin(X);
index = find(X==10);
Y_point = Y(index)
% See graphically
plot(X,Y,X(index),Y_point,'o')
my question is now how to mark for x value 10 to 11

Best Answer

clc; clear all ;
X = 1:0.1:20;
Y = sin(X);
index = find(X==10);
Y_point = Y(index)
% See graphically
plot(X,Y,X(index),Y_point,'o')
hold on
% plot X in the range 10 to 11
Xi = X(X>=10 & X<=11) ;
Yi = Y(X>=10 & X<=11) ;
plot(Xi,Yi,'*k')
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