| Lag and A_Correlate/C_Correlate [message #67138] |
Mon, 06 July 2009 15:12 |
Max
Messages: 2
Registered: July 2009
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Junior Member |
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Please excuse the incredibly uninformed nature of this post; I have no
training in IDL, scientific programming, or really programming at all.
I'm asking on behalf of a friend who is, I think, too stubborn to do
so herself (she has received some training, but by entirely
unmotivated and unhelpful grad students who are, it seems, useless).
Here's the situation:
There are two large sets of data (n≈90,000) for which my friend needs
to be able to find the auto-correlation and cross-correlation
functions. both A_CORRELATE and C_CORRELATE involve the lag parameter,
the function and nature of which we cannot readily identify. The final
result of this work is to be a plot (I believe) of correlations, or
possibly a function serving the same purpose (although, it strikes me
that with a discrete number of data points, the plot and the function
would be equally useful). I've searched the internet, but not knowing
the first thing about the language has really hampered this.
We would both be very grateful if someone could help clear up these
questions: firstly, what does lag measure? Secondly, how does the lag
parameter affect the output of the A_CORRELATE and C_CORRELATE
functions? Thirdly, what can my friend do to get this to work?
One idea I've had from searching the internet include creating an
array of size n (perhaps F=findgen(n), where n≈90,000) and trying
C_CORRELATE with something like "lag = [-F, F]". Is this at least on
the right track?
Any help at all would be greatly appreciated. Thanks.
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