Why do I receive and error message for the negative in my function?

I am trying to input a function but everytime I run my script the negative on the first x gets an error mesage that says invalid use of an operator. I am not sure how else to rewrite the function so that the x is still negative.

g = @ -x.^3 + 4*x.^2 - 3

Answer 1

[Dyuman Joshi]

The syntax for defining anonymous functions is -

f = @(list_of_independent_variables) relation_of_indepent_variables;

So for your case, it would be -

g = @(x) -x.^3 + 4*x.^2 - 3;

And to find the value of the function for a particular value, just plug it into the handle -

g(-3)

ans = 60

g(6.9)

ans = -141.0690

Read more here - https://in.mathworks.com/help/matlab/matlab_prog/creating-a-function-handle.html#buvu9u8-1

https://in.mathworks.com/help/matlab/ref/function_handle.html

[Dixon]

Oh so my main problem was not having the (x) after the @ symbol not necessarily the fact that the variable was negative?

[Stephen23]

"Oh so my main problem was not having the (x) after the @ symbol not necessarily the fact that the variable was negative?"

Correct. See:

https://www.mathworks.com/help/matlab/matlab_prog/anonymous-functions.html

[Walter Roberson]

g = @x.^3 + 4*x.^2 - 3

would not be a syntax error. It would mean to take the handle to a function named x and to attempt to cube the function handle. You cannot do mathematics on a function handle so you would get a runtime error... but not a syntax error.