Integrating using quad

Hi, I have this really simple problem regarding using quad to integrate a function

for example, I would like to integrate x^2 from 1 to 4 so I would type in:

quad(x^2,1,4)

and this results in an error

then I try:

quad(vectorize(x^2),1,4)

ans =

    21

Perfect!

But vectorizing x^2 resulting in:

vectorize(x^2) ans = x.^2

however typing quad(x.^2,1,4) into matlab still returns an error.

Why is that so?

Answer 1

[Walter Roberson]

Is x declared as a symbolic variable? quad() cannot process symbolic expressions as the function.

If x is not a symbolic variable, then what is it? vectorize() can only be applied to character strings, inline objects, or function handles.

quad('x^2',1,4)

would be valid syntax, but would run in to problems because quad needs the expression to be able to handle vectors.

quad('x.^2',1,4)

would be valid.