Derivative using datenum format vector

Hi everyone,

I am trying to calculate a derivative using (y2-y1)/(x2-x1) thus I am using: gradient(x) ./ gradient(t). The problem is that the vector (t) is in a datenum format therefore when I use the formula the results become incorrect as it do not respect the fact that they in reality are dates.

My intention is to have (y2-y1)/(t2-t1) where the time is in minutes (with respect to seconds as well).

How do I solve this?

Answer 1

[Steven Lord]

Use the minutes function to compute the difference between two elements of a datetime array (or two datetime arrays) in terms of a number of minutes. This example is contrived, since I know what m should be, but you could use this with t1 and t2 read in from a file or obtained some other way than computation.

t1 = datetime('now');
dt = randi([30 150]) % 30 to 150 minutes
t2 = t1 + hours(dt/60);

m = minutes(t2-t1) % effectively the same as dt