MATLAB: Display actual and estimate values of cube root

while loop

In the attached document, my actual value of the cube root and also my estimated value come out the same. Can someone please take a look at my script?

Best Answer

Look at your code:

fprintf('The actual cube root is %0.3f\n', Estimate)
fprintf('The estimate of the cube root is %0.3f\n', Estimate)

You are printing the same value twice. You never calculate the "actual" cube root.

Even if you did calculate the actual cube root, would you be able to see the difference within the 3 decimal places that you print out?

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Nick - your answers come out the same since you are writing out the same variable for each print statement:

 fprintf('The actual cube root is %0.3f\n', Estimate)
 fprintf('The estimate of the cube root is %0.3f\n', Estimate)

The actual cube root of the input number would be

 fprintf('The actual cube root is %0.3f\n', x^(1/3));

where x is the number that you are trying to compute the cube root of. For example,

 x = input('Please enter a number:');

will allow the user to enter a number that he or she wishes to find the cube root of. Note that in your code you do

 CubeRoot=input('Please enter a number:')

The above line is misleading since the number entered by the user is not the cube root but is the number that they wish to find the cube root of.

MATLAB: How do you enter the command for a cube root

Two simple options:

x^(1/3)

Or,

nthroot(x,3)

Be very careful though. If x is negative, it will return a complex number, because there are indeed THREE cube roots of a negative number. Two of them are complex. nthroot will give you the root you would expect however.

(-2)^(1/3)
ans =
      0.62996 +     1.0911i
nthroot(-2,3)
ans =
      -1.2599

In your case, it is not relevant, since the number will be non-negative.

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MATLAB: How do you enter the command for a cube root

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