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Offline adiaz  
#1 Posted : 02 October 2012 08:13:52(UTC)
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Hessian example.
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on 02/10/2012(UTC)

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Offline uni  
#2 Posted : 02 October 2012 09:27:02(UTC)
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Offline adiaz  
#3 Posted : 02 October 2012 10:16:45(UTC)
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Check this.
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Offline uni  
#4 Posted : 02 October 2012 10:36:06(UTC)
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It is not a good idea to use smath subscripts in maple. Here I need to think a little bit.
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Offline adiaz  
#5 Posted : 02 October 2012 11:35:18(UTC)
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Nice bug. This a workaround.
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Offline adiaz  
#6 Posted : 06 October 2012 10:17:29(UTC)
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I think that this is the better way to work with the Jacobian.

Alvaro.
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Offline omorr  
#7 Posted : 06 October 2012 14:24:02(UTC)
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Hello Alvaro,

But what to do if the vector function is defined this way?

Φ(X,t):-5*t*mat(el(X,1),el(X,2),2,1)+mat(el(X,2)*el(X,1)^2,el(X,2)^2*el(X,1)^2,2,1)

It will not work until t is a constant (scalar). Take a look at the pictures please.

Regards,
Radovan

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Offline adiaz  
#8 Posted : 06 October 2012 22:26:35(UTC)
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What doesn´t works is length, so can't include symbolic scalars outside vectors.

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Offline omorr  
#9 Posted : 07 October 2012 09:40:21(UTC)
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Hello Alvaro,

Actually, that is the point. I think that's the problem of the symbolic engine.
The first one gives the symbolic result

(-5*t)*mat(el(X,1),el(X,2),2,1)+mat(el(X,2)*el(X,1)^2,el(X,2)^2*el(X,1),2,1)=mat(-5*el(X,1),-5*el(X,2),2,1)*t+mat(el(X,2)*el(X,1)^2,el(X,2)^2*el(X,1),2,1)

and the result is not a vector, therefore length() does not work.
The second one actually give you the vector symbolically

(-5)*mat(el(X,1)*t,el(X,2)*t,2,1)+mat(el(X,2)*el(X,1)^2,el(X,2)^2*el(X,1),2,1)=mat(el(X,1)*(-5*t+el(X,2)*el(X,1)),el(X,2)*(-5*t+el(X,2)*el(X,1)),2,1)


Maybe the solution would be to say in advance what the variable t was - either scalar, vector or matrix. Something like "assume". If SMath assumed that t was a scalar, it should behave in accordance to that and give you the second correct result.

Regards,
Radovan
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