# How to do numerical integration from data set?

Posted 9 years ago
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 How to do numerical integration from a data set?
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Posted 9 years ago
 How do I import excell data to mathematica and inverse
Posted 9 years ago
Posted 9 years ago
 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
Posted 9 years ago
 Use the Chop command. http://reference.wolfram.com/mathematica/ref/Chop.htmlOr you can use Re to get the real part of the complex number.
Posted 9 years ago
 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 9 years ago
 Strongly related SE thread: How to integrate functions of linearly interpolated data?
Posted 9 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}]
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