Matlab - convert vector to discrete function

How can I convert a vector of real numbers to a discrete function dependent on other vector of real numbers:

U(i); i=1,2,3... ---> U(x); x=[0.01,0.003,0.0036...]

*The desired function is the function I get from: >>plot(x,U); *The final goal is to integrate : U(j+1)=integral(U(x)*5^.x,-0.05,0.05);

[Babak]

How come the first U has inputs of integer numbers but the second U has input of x? I mean what's the relation between x and i? You also need to mention what U is where is came from...

Answer 1

[Matt Fig]

You can fit a polynomial to U, or a spline or any function. We must know what the expected relation is, or at least see the graph to have a hope of figuring out the relationship.

Perhaps you could post an image of the plot.

You also can simply use TRAPZ without any fitting.