First I have seen that perhaps my question has an answer in AskSagemath but
currently it doesn't answer.
Suppose I have a list of variables x_1, x_2, x_3,...x_n
I have some sub-list of variables say [x_4, x_1, x_6...]. But whenever x_4,
x_5,x_6 belong to this list I want the substitution x_4
Am I missing something here?
sage: F. = FunctionField(QQ)
sage: f = F.random_element()
sage: f
(-p^2 + 5*p)/(-2/9*p^2 + 54)
sage: f.subs({p:3})
(-p^2 + 5*p)/(-2/9*p^2 + 54)
I have an element f of a rational function field F in one variable and
want to "evaluate" it at a value of the variable
hi,
i've encountered a problem in performing substitution in ExteriorAlgebra.
i have
E.x,y=ExteriorAlgebra(QQ)
and i'd like to perform the substitution, e.g., {x:y} on any expression
representing an element in E: for example,
x.subs({x:y})
but it returns x, meaning the substitution is not
I have the following code, which produces a list of polynomials in the
infinite number of variables e_0, e_1, ...
M.e = InfinitePolynomialRing(QQ, implementation=sparse)
S.z = LaurentSeriesRing(M)
Qxy.X,Y = PolynomialRing(QQ)
a=var('a')
b=var('b')
k=var('k')
L=[]
n=6
x = 1/z^2 +
sage: K.d,e,p,g,m,f,u,v,j,N =
FractionField(PolynomialRing(QQ,10,'depgmfuvjN'))
sage: R.s = K[]
sage: w=u
sage: u=0
sage: w
u
Why doesn't Sage answer 0 for the value of w here? More generally, if I
have some complicated expression and I assign a value to one of its
variables,
Sage knows
Is there a reason why integers are treated so differently to variables?
If, for example, 2 is replaced by a variable, everything works as expected:
h = (k1 + k2)*x
h.subs_expr(k1 + k2 == k3)
k3*x
I don't understand why g is expanded to
2*k1 + 2*k2
but h not to
x*k1 + x*k2
Is there no way
Hello everyone,
there seems to be a bug in substitute:
var('k1 k2 k3')
f = (k1+k2)^2
f.substitute(k1+k2==k3)
gives k3^2 as expected.
var('k1 k2 k3')
f = (k1+k2)*2
f.substitute(k1+k2==k3)
gives 2*k1 + 2*k2. The same happens for +2 instead of *2.
Is there an alternative to do a substitution?
Hi Stefan,
On Mon, 25 Jan 2010 06:49:55 -0800 (PST)
Ichnich warm...@web.de wrote:
there seems to be a bug in substitute:
var('k1 k2 k3')
f = (k1+k2)^2
f.substitute(k1+k2==k3)
gives k3^2 as expected.
var('k1 k2 k3')
f = (k1+k2)*2
f.substitute(k1+k2==k3)
gives 2*k1 + 2*k2. The
I have the following problem : I have two nested functions
a=lambda x: 2*x
b=lambda x: a(x)^2
Everything goes well as long as I want to compute the derivative of b
but how can I evaluate this derivative at x=2.
I tried
g=lambda x: diff(b(x),x)
g(x) returns 8*x as expected
but g(2)=0.
In other
Hi,
On Thu, Jan 21, 2010 at 2:14 AM, Stochastix
laurent.decreusef...@gmail.com wrote:
SNIP
In other words, how can we substitute x=2 to the expression 8*x ?
I guess this is somewhere in the docs but I didn't find where.
Is the following what you want?
[mv...@mod primroots]$ sage
I'm trying to figure out how to do a simple substitution. I've the
following code:
var('r beta beta_0 R a h')
psi=function('psi',r)
sigma=function('sigma',r)
H_0=function('H_0',r)
H_grad = lambda psi : (1/2)*(beta/beta_0)*R^2*(psi.diff(r))^2
H_0(psi) = -(1/2)*(beta/beta_0-1)*psi^2 +
Hi,
I have some equations that use the Greek letter lambda in them, but
I'm having problems because lambda is a keyword in python, and at some
points the two collide. For example:
sage: l = var(lambda)
sage: t = var(theta)
sage: e1 = t == l^2
sage: e2 = e1.solve(l)
sage: e1
theta == lambda^2
Hi,
I keep running into a road block which I think means either I'm
missing something simple, or I'm thinking about things the wrong way.
I'm fairly new to sage, and CAS in general, so either is possible.
Here's a simple example of what I'm doing.
Lets give ourselves two symbolic equations:
Hi,
I'm fairly new to sage with some background in maxima.
My workbook is shared at
http://www.sagenb.org/home/pub/410/
the last three lines show the error I get.
Basically, I derive an equilibrium condition that I would like to use
in the previous stage of my game (solving by backwards
Hi,
What is the easiest way to make a mathematical substitution in Sage?
For example: We have
eqn1 = F == a + b
and would like to use a = 0 and b = 3 to calculate F.
Should I use solve and treat the problem like a system of equations,
or is there a substitute-like command?
Regards,
hpon
Hey all:
I'm back with a follow up question on the topic of substitution in
Sage. How can i work the following example? I have an expression
that involves the derivative of a function, and into that expression i
want to substitute the value of the derivative. Simple, eh? I tried
Mike's **
Hello,
Suppose I have a symbolic matrix:
sage: m = matrix([[a,b],[d,e]])
and I wish to substitute some or all elements of m with numbers.
The obvious
sage: m.substitute(a=1)
returns
[a b]
[d e]
so the substitution (which works fine on a list) does not work on a
matrix.
How do I do such
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