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Some Easy (hopefully) Questions
*To*: mathgroup at christensen.cybernetics.net
*Subject*: [mg2030] Some Easy (hopefully) Questions
*From*: Rob Carscadden <carscadd at pps.pubpol.duke.edu>
*Date*: Sat, 16 Sep 1995 01:40:17 -0400
*Organization*: Duke University, Durham, NC, USA
I'm trying to run a model using Mathematica. I've scoured all our
libraries and all the books are gone. Working with all too basic
Mathematica By Example, I haven't been able to find how to do some rather
easy things.
The first thing I want to do is find a max (I need to plug the max and
where it occurs into anther equation). I have a function, and I have
taken both the first and second derivatives. I solve for f'(x) = 0. But
here's where the trouble comes in. I want to plug these points back into
my f(x). How can I do this. Look at the following example:
possmax = Solve[(x - 1)^2 == 0,x] // N
I get {{x -> 1.},{x ->1.}}
and when I try
possmax[[1]]
I get {x ->1.}
but I want the number 1 instead.
I know this if probably extremely basic, but due to lack of available
documentation here, I can not figure it out.
P.S. another useful trick to know would be how many objects are in a
list. My function a bit more complicated (compositions, logs etc.), and I
don't exactly how many solutions I will have from the Solve[ ] statement.
--
Rob Carscadden
carscadd at pps.duke.edu
http://www.duke.edu/~cars
49% of all Statistics are made up on the spot!
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