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How to do numerical integration from data set?

Posted 10 years ago
    How to do numerical integration from a data set?
7 Replies
How do I import excell data to mathematica and inverse
When I integrate using the definite integral symbol in conjunction with the N symbol I get a small complex numerical in addition to the correct answer. What does that mean and what action is necessary.
Luke
Use the Chop command.

http://reference.wolfram.com/mathematica/ref/Chop.html

Or you can use Re to get the real part of the complex number.
POSTED BY: Sean Clarke
What it means is that during the calculation there were two complex intermediate results whose imaginary components almost cancelled.

If the calculation were done with exact numbers (Integers and Rationals), the imaginary components would have exactly cancelled.
POSTED BY: Bruce Miller
Posted 10 years ago
Look up Interpolation and NIntegrate.  Here is an example:
fun = Interpolation[{{0, 0}, {0.1, .3}, {0.5, .6}, {1, -.2}, {2, 3}}]

NIntegrate[fun[x], {x, 0, 2}]
POSTED BY: David Reiss
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