y-values from a given function

I have a function and two values of x and I would like to find the values corresponding to the x-values, how should I start ? I was thinking to do for loop but it does not work it only gave me one of the answers (as you can see below)!

for x = 0.36 : 0.40
     y = x^4 + 5*x^2 + sqrt(x-1)  
end

y =

   0.6648 + 0.8000i

[John D'Errico]

So your code was wrong. Show your code, and someone will show you how to fix it.

Answer 1

[John D'Errico]

Ok, you posted your code.

As I expected, every time through that loop, you overwrote the previous values.

Worse, what do you think 0.36:0.40 does? It generates a set of values from 0.36 to 0.40 in increments of 1 (ONE)! How many values do you think that creates? ONE: 0.36.

Simplest is to not use a loop.

x = [0.36, 0.40];
y = x.^4 + 5*x.^2 + sqrt(x-1);

Note the use of .^ there. It is there for a reason. Learn about element-wise operations on a vector or array.

help power

[Yumi Lee]

OMG ! so using loop was useless lol Thank you so much that helps a lot :)

[Yumi Lee]

But why this does not work if I have something such as (x-1) multiply by the square root ? It says '' Error using * Inner matrix dimensions must agree.'' Any idea ?

[Stephen23]

You probably want to use element-wise multiply .* rather than matrix multiply *. Read about the differences here:

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

[Yumi Lee]

ok I will try it. Thank you