| Re: Finding a Tangent line [message #42653] |
Sat, 19 February 2005 06:36 |
Chris Lee
Messages: 101
Registered: August 2003
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Senior Member |
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In article <1108750898.355794.131660@l41g2000cwc.googlegroups.com>,
"AMandra@gmail.com" <AMandra@gmail.com> wrote:
> I'm very new to IDL, so I apologize if this is simple problem. I'm
> doing research involving infrared images of Mars. A graph of pixel
> saturation will be linear than go cubic to a zero slope as it saturates.
> However, the test in the program we run doesn't seem to work with some
> images that were given extra current. What I'd like to do is test the
> slope of the tangent line until it goes towards zero for saturation,
> however I'm not sure how to do this and I can't make heads or tails of
> the help file on DERIV or anything else I think would be helpful. The
> fit is being taken with polyfit. I appreciate any help, and I'm sorry
> if that was extremely vague.
A graph of pixel saturation against what will be linear? If it's a graph
of pixel saturation versus current. Plot the data? Assuming you have that
data, i.e.
plot, current, pixel_value
but you don't say what data you have, or what the test program is.
Chris.
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