## 35 Reputation

12 years, 119 days

## How to create a function of a function?...

Maple 15

Hi everyone,

I would like to do:

`f:=unapply(x**2,x);j:=unapply(2*f(x),f(x));`
` `
`Basically it is to define j(f(x))`
`But this is doesn't work. What is the right way to do it?\`
` `
`My final goal is to calculate int(j(f(x)), f(x)=-infinity..infinity).`

## Integral over a vector...

Maple

Hi everyone,

Is it possible to perform an integral over vector without writing a multiple integral over each component?

I am integrating over a vector of dimension 12, so I am trying to find another way to calculate rather than writing 12 integrals.

Thanks

## Singular covariance matrix...

Maple

Hi everyone,

I want to create a Gaussian PDF so I need to calculate Determinant(sigma) with sigma the covariance matrix of a gaussian variable.

If we call this variable alpha (which is a 12 dimension vector and represents the noise in a discrete dynamical equation), then sigma_ij=ExpectedValue(alpha_i*alpha_j)-ExpectedValue(alpha_i)*ExpectedValue(alpha_j)

and this is zero most of the time! So the covariance matrix is singular and the determinant is zero.

## Brownian Motion_Mean not zero...

Maple 15

Hello everyone,

I have a problem with the Brownian Motion (I'm using Maple 15).

Here is the code:

X:=BrownianMotion(0,0,1,t);

X1:=SamplePath(X(t),t=0..T,timesteps =T/d):

Mean(X1);

The last line give me a number different from zero, which is not true for a Brownian Motion as defined.

Could you please tell me where is the problem?

PS: I have the same problem with WienerProcess(sigma).

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