[Tutor] Rate transition from 60hz to 1000hz

[Alan Gauld]

On 10/05/16 04:08, David Wolfe wrote:

> I'm collecting both video and force plate data, and I need to be able to
> synchronize the two, so I can make some calculations.  The video data is at
> 60hz, and the force plate data is at 1000hz.  I don't want to truncate the
> force plate data.

I have no idea what force plate data is but assuming it's nothing
special you have two sets of data, one at 1000Hz and one at 60Hz.
And you want to join them together at the appropriate points.

The problem is that 60 is not an exact factor of 1000 so you
will need to decide how you align the samples.

> So, how do I perform a rate transition (or interpolation, or whatever) to
> expand the data that is captured at 60hz to be able to synchronize it with
> the data that has been captured at 1000hz?

Interpolation over such a large sample range is tricky and risky.
The simplest way is to assume a straight line between samples.
So each interpolated value is just S2-S1/17 higher than the
previous value(S1).

A better way is to try to determine the current curve shape and apply
that. But it's much harder to do unless you know what kind of data to
expect!

> Also, if I'm not using the correct terms, please let me know.  I'm new to
> Python and programing, and I'm trying to learn as fast as i can.

This has nothing to do with Python or even programming per se.
Its really a math question. The same issues would apply if you
were tabulating the data by hand on paper.

That having been said, there may be some math libraries around
that you could use to do the sums for you. But it's not my area of
expertise so maybe some of the other tutor members will suggest
something in numpy or pandas or whatever.

-- 
Alan G
Author of the Learn to Program web site
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