Tomas's profile - activity

I'm trying to get the syntax highlighting to work in emacs. I have tried to install sage-mode following the manual on the https://bitbucket.org/gvol/sage-mode/...

This fail on running the first command: $ sage -f sage_mode with error message sage-run received unknown option: -f

I use Sage Version 5.9.

Could someone help me with this please?

I have the same problem. My equations are way too long to be shown on one line in pdf file. I have tried to export it to LaTeX and split manually, but it is not an easy job to do. Have you found any solution for that?

Anyway, I reckon that the first example is probably a bug. The derivative of n-dimensional vector should have n-dimensions again no matter to which ring it belongs to. Would you know how to report that, please?

Look at the help of derivative. It works on symbolic functions, polynomials, and symbolic expressions. Your variable u is not a function, so it is not really being considered a two dimensional symbolic expression or function. If you do

sage: u(x,y) = matrix(1,2,[-1,1])
sage: derivative(u, x)
(x, y) |--> 0

then you can see that it is considering it as a two dimensional function. In the second case, you have a function of one variable in the variable x.

The alternative fix is to work in the symbolic ring:

sage: u = matrix(SR, [-1,1])
sage: derivative(u,x)
[0 0]

Thanks, the fix with a symbolic ring is helpful. In my problem the $\vec{u}$ really is a function, just happens to be a constant at this occasion.

Compared to: a(x) = function('a',x) b(x) = function('b',x) u = matrix(1,2,[a,b]) r = derivative(u,x);r Which gives a vector as expected: [x |--> D[0](a)(x) x |--> D[0](b)(x)]

Trying to obtain the derivative of $\vec{u} = [-1,1]$ using the following code:

u = matrix(1,2,[-1, 1])

r = derivative(u,x); r

I get a scalar value 0.

Although according the following relation it should be a 2-dimensional zero vector.

$$\frac{\mathrm{d} \vec{u}}{\mathrm{d} x} =\frac{\mathrm{d}}{\mathrm{d} x} [-1, 1] = [ \frac{\mathrm{d}}{\mathrm{d} x}(-1), \frac{\mathrm{d}}{\mathrm{d} x}(1) ] = [0, 0]$$

Why does it happen? In the case it's a bug where could I report it?

Thanks

So an solution which work is to convert the vector to a list, append the new variable and convert to a vector again. The code for that would be as follows:

u = x.list()

u.append(sigma)

u = vector(u)

Do you see any potential problems with this solution? Why there is no method append in vector? Could I do better?

I would like to define a new vector in Sage $\vec{u} = [O, P, \sigma]$ using a previously defined vecotor $\vec{x} = [O, P]$ and a new variable $\sigma$.

My code looks like:

var(’O, P');

var('sigma');

x = vector([O,P]);

u = vector([x, sigma]);

Which gives an error:

TypeError: unable to find a common ring for all elements

Apparently this is because vector() requires the variables to be of the same ring. In my case

x.parent()

Vector space of dimension 2 over Symbolic Ring

and

sigma.parent() Symbolic Ring

There is any way how to connect this two objects ($\vec{x}$, $\sigma$) together to create one vector?