MATLAB: It is possible to read the graph and it has to produce the Y value for the input X value.

read the graph and it has to produce the y value for my input x value

This is what my program to create a graph.. now i want to read the graph and it has to produce the y value for my input x value. is there any syntax for that?
j=input('Enter the number of straight lines in the graph: ');
for i=1:j
    disp('Enter the X Y co-ordinate of one end of the straight line:');
    x1(i)=input(' '); 
    y1(i)=input(' ');
    disp('Enter the X Y co-ordinate of another of the straight line:');
    x2(i)=input(' '); 
    y2(i)=input(' ');
    c(i)=input('Enter the Y-intercept for straight line: ');
    m(i)=(y2(i)-y1(i))/(x2(i)-x1(i));
end
for i=1:j
    x=x1(i):0.01:x2(i);
    y=((m(i))*x)+c(i);
    plot(x,y);%,'MarkerFaceColor','g');
    hold on;
    %axis([-10 10 -5 5])
end
disp('-----------------------');
disp('your graph is displayed');
disp('-----------------------');
disp('Enter the X value from your graph: ');
p=input(' ');
disp('Corresponding Y is: ');

Best Answer

Why are you asking two (x,y) values for a line and then also the intercept? Given two points you are able to calculate both m and c. And that point you will have the equation y of your line that you can evaluate to find the corresponding Y.
If you have more lines you may consider including and IF-ELSE statement, check what is the X value, associate it to the corresponding equation and then evaluate the equation. As Walter pointed out you may have multiple Y values, you may prevent this by checking that the user is using different X ranges when creating the curves.
Related Question