Yes, this completely solves my issue. Thanks! On Monday, April 17, 2017 at 8:33:44 PM UTC-4, David Joyner wrote: > > On Mon, Apr 17, 2017 at 7:53 PM, David White <[email protected] > <javascript:>> wrote: > > Hello, > > > > I am trying to use Sage in my class with some basic problems about > matrices. > > Several of the problems in the book are of the form “find all values of > k > > such that … is consistent” where the … is some linear system where k > > appears. If doing these problems by hand, one would take the determinant > and > > solve for the values of k where the determinant is not zero. Sometimes > the > > linear system is large, so I want to be able to use the .determinant() > > command (or .echelon_form() for similar problems) on a matrix where k is > an > > Is this an example of what you want? > > sage: k = var("k") > sage: A = matrix(SR, [[-1,20],[20,k]]) > sage: det(A) > -k - 400 > sage: solve(det(A)==0,k) > [k == -400] > > > > element. However, Sage is not letting me create such a matrix object, > > because it does not recognize my assume() command telling it that the > > variable k is rational (or real, for that matter; neither works). > > > > I’m trying to mimic what is going on here: > > > http://doc.sagemath.org/html/en/reference/calculus/sage/symbolic/assumptions.html > > > > > When I type the following code, I get an error saying Sage is "unable to > > convert k to an element of a rational field" (I get this error with and > > without the assume()) > > > > var('k') > > assume(k,'rational') > > v = vec(QQ,[k,k,k]) > > > > Can someone please tell me how to make variables and matrices play > nicely > > together? > > > > -- > > You received this message because you are subscribed to the Google > Groups > > "sage-support" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to [email protected] <javascript:>. > > To post to this group, send email to [email protected] > <javascript:>. > > Visit this group at https://groups.google.com/group/sage-support. > > For more options, visit https://groups.google.com/d/optout. >
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