Simplify expression after collect function

Question

Tom Klijn 2016-2-12

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/267855-simplify-expression-after-collect-function

回答： Walter Roberson 2016-2-12

Hello I have written a code that performs newton interpolation. After I determined the coefficients I want to display the simplified expression like this: p(x) = p14*x^14 + p13*x^13 + ... + p0

But when I use the collect function it displays the result as follows:

((1613572414787747*13^(1/2)*17^(1/2))/1667355148462087077893881565539536391777188164935759167488 + (1613572414787747*22^(1/2))/2157753721539171512568552614227635330535184684034511863808 + 3914999446024239438846407105870793530675/11373727500204176163375146989836406690440670303259304015465585573888)*X^14 + ...

I would like to display 3.4421e-28*X^14 + ...

How do I do that?

This is the code I used to create formula out of th calculated cofficients:

%display the formula (collect or factor function)
syms X;
p_x = collect( a(1)...
  + a(2)*(X-x(1))...
  + a(3)*(X-x(1))*(X-x(2))...
  + a(4)*(X-x(1))*(X-x(2))*(X-x(3))...
  + a(5)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))...
  + a(6)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))...
  + a(7)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))...
  + a(8)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))...
  + a(9)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))*(X-x(8))...
  + a(10)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))*(X-x(8))*(X-x(9))...  
  + a(11)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))*(X-x(8))*(X-x(9))*(X-x(10))...
  + a(12)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))*(X-x(8))*(X-x(9))*(X-x(10))*(X-x(11))...
  + a(13)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))*(X-x(8))*(X-x(9))*(X-x(10))*(X-x(11))*(X-x(12))...
  + a(14)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))*(X-x(8))*(X-x(9))*(X-x(10))*(X-x(11))*(X-x(12))*(X-x(13))...
  + a(15)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))*(X-x(8))*(X-x(9))*(X-x(10))*(X-x(11))*(X-x(12))*(X-x(13))*(X-x(14))...
  + a(16)*(X-x(1))*(X-x(2))*(X-x(3))*(X-x(4))*(X-x(5))*(X-x(6))*(X-x(7))*(X-x(8))*(X-x(9))*(X-x(10))*(X-x(11))*(X-x(12))*(X-x(13))*(X-x(14))*(X-x(15))...
, X )