MATLAB: Dont matlab answers match theoretically calculated answers

logictheoretical

Hi,

Ive been asked to explain why the answers I obtain from MATLAB of the step and impulse response is different from the mathematical equations/solutions. Any ideas why there is a difference??

Best Answer

MATLAB does not use infinite precision like theoretical calculations do.

http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

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MATLAB: How to get the Exact answer from this

That is the precise number, to the accuracy of the input values (which were probably not very accurate at all.)

Remember that rational numbers are infinitely precise. You cannot do better than infinitely precise.

You might have expected to see a floating-point number, but floating point is inherently inaccurate for most calculations.

You can see an approximate value of solution by using double() or vpa(). The result is guaranteed to not be precise.

By the way, that denominator is 2^244

MATLAB: Maclaurin series for ln(x) and ln(x+1)

Maclaurin series is just a Taylor series expanded at x = 0. For ln(x) the series does not exist. For ln(1+x), try the following

syms x
y = log(x + 1);
y_series = taylor(y, x, 0, 'Order', 10)

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MATLAB: How to get the Exact answer from this

MATLAB: Maclaurin series for ln(x) and ln(x+1)

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