extracting values at set intervals from a vector

From the following vector:

depth = [0:0.1:20];

How could I create a new vector that had the same data as 'depth' but a value taken every 0.5, providing an outcome of:

d2 = depth(1:5:end);

Since my data is not actually spaced at 0.1 intervals but at randomly distributed intervals I cannot apply the simple approach shown above. What would be the best methods of achieving this?

Answer 1

[Jan]

Use interp1 for a linear interpolation.

[Richard]

Is there another way o doing this, the overall aim of what I am attempting to achieve is to measure the uncertainty of interpolation methods. Isn't there a method for taking the first value and then every value in the vector which is + 0.5 of the last? maybe use floor if they are not exact?