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Collect

  • Collect[ expr , x ] collects together terms involving the same powers of objects matching x.
  • Collect[ expr , , , ... ] collects together terms that involve the same powers of objects matching , , ... .
  • Collect[ expr , var , h ] applies h to the expression that forms the coefficient of each term obtained.
  • Collect[ expr , x ] effectively writes expr as a polynomial in x or a fractional power of x.
  • Examples: Collect[x + n x + m, x]; Collect[(1+x+y)^3, x].
  • Collect[ expr , x , Simplify] can be used to simplify each coefficient separately.
  • See the Mathematica book: Section 1.4.5Section 3.3.1.
  • See also: Series, CoefficientList, Together, Cases.

    Further Examples

    These two inputs collect terms first in the variable x and then in the variable y.

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    This first collects with respect to x, then collects coefficients with respect to y inside of each of the x coefficients.

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    In this example we use Collect to rewrite an expression by pulling out factors common only to certain parts.

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    This example has the usual two arguments.

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    Collect applies an optional third argument to the innermost coefficients of the collected terms.

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    Suppose you want to collect all the products of powers of x and y in a polynomial that involves other variables. One way is to use patterns.

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    Another way is to use MonomialList.

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