the magnitude of y-axis in a ksdensity plot

Dear all,

Can you explain the meaning of magnitude of y-axis in a plot using ksdensity function?

Thank you very much.

Answer 1

[the cyclist]

The output of ksdensity() is an estimate of the probability density function.

It's the function f(x) such that

f(x) * dx

is the probability of a randomly selected value from the distribution being in that particular interval of x.

People are sometimes confused by the fact that the output of ksdensity doesn't sum to 1. You have to remember to multiply by the interval width. Then it will.

[Nguyen]

Dear Mr. the cyclist,

Thank you very much. You help me a lot.

Nguyen.

[Nguyen]

Dear

Could you please give some ideas regarding one more question: In the function f(x) above, if x is time, concentration, ... why in the output of ksdensity(), x can be minus?

Thank you very much.

[the cyclist]

MATLAB doesn't know that negative values of x don't make physical sense.

But you can tell the function not to allow negative values by using additional arguments:

[f xi] = ksdensity(...,'support','positive')

See the documentation for details.

[Nguyen]

Thank you very much. You help me a lot. Wish you have a good weekend.