两个向量x和y。 如何指向y中的最大元素并选择x中的相应元素？

Question

I have two vectors x_values and y_values , each of the same length but y_values is computed from the x_values . How can I take the maximum element in y_values and pick its corresponding element in x_values ?

For example if the maximum element in y_values is 31 , the program should return its corresponding value in x_values as 5 . Here is my effort:

function maxValue = maximumValue()
x_values = -5:5;
y_values = [];

for i = x_values
    y = i^3 - 3*i^2 - 3*i - 4;
    y_values = [y_values, y];
end

for j = 1:length(y_values)
    if max(y_values(j))
    maxValue = x_values(j);
    end
end

end

Answer 1

>> x_values = -5:5;
>> y_values = x_values.^3 - 3 * x_values.^2 - 3 * x_values - 4;
>> [ymax, index_ymax] = max(y_values);
>> disp(x_values(index_ymax))

.^ is an element-wise exponentiation.

max() can return two values. First one is the maximum value, and the second one is its corresponding index.

>> help max
max    Largest component.
    For vectors, max(X) is the largest element in X. For matrices,
    max(X) is a row vector containing the maximum element from each
    column. For N-D arrays, max(X) operates along the first
    non-singleton dimension.

    [Y,I] = max(X) returns the indices of the maximum values in vector I.
    If the values along the first non-singleton dimension contain more
    than one maximal element, the index of the first one is returned.

And my suggestion is more MATLAB-ish.