take a value y of a function y = f(x) giving x.

Suppose we have the following code that creates the graph of the sine function:

x = 0:pi/100:2*pi;

y = sin(x);

plot(x,y)

Now I have the graph of the sine function. how can I get the value of the function by specifying the respective x-value? For example, how can I get the value of sin(51) based on the plot I created (it is not valid to use the matlab sine function)?

Answer 1

[Star Strider]

Use an appropriate interpolation function, such as interp1 or just index into it, depending on what you want to do —

x = 0:pi/100:2*pi;
y = sin(x);

y51 = y(51);

plot(x,y)
hold on
plot(x(51), y(51), 'ms')
hold off
axis('padded')

.