# How to take an equation as input from user and read the coefficient from it?

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Sourin Dey on 27 Dec 2016
Answered: Walter Roberson on 27 Dec 2016
How to take an equation as input from user and read the coefficient from it?
KSSV on 27 Dec 2016
What equation? Can you give an example?

Walter Roberson on 27 Dec 2016
If you have the Symbolic toolbox, then you could convert the string representing the equation to a function handle using str2func() and then you could pass symbolic arguments to it to get a symbolic representation of it.
At that point, if the equation is known to represent a polynomial, then you can use coeffs() to get the coefficients.
If the equation is not known to represent a polynomial then you can use children() to break it into pieces, and examine the pieces using symvar() to determine whether they contain the variable of interest. However, in such a case it gets tricky to define what the coefficients are. For example, for sin(2*x) it is not really correct to say that the coefficient of x is 2.