Tag Info

New answers tagged

1

It appears that 1879 is correct. Cofactor[a,{1,1}] is equivalent to Det[a[[2 ;;, 2 ;;]]], which is 1879. More generally, Cofactor[a,{i,j}] is equivalent to Det[Drop[a, {i}, {j}]]*(2*Mod[i*j, 2] - 1) The second term here accounts cofactors for the fact that the even positions of odd rows (and the odd positions of even rows) are the negative of the ...


1

The book A Mathematical Introduction to Robotic Manipulation talks about kinematic and dynamic modeling for manipulators based on Screw theory. It provides a Mathematica Package for Screw Calculus. I find it quite useful.


3

Here is an example of how to do it. We need xTensor and xCoba packages. First is made to work with abstract objects, whilst the second is for operations with explicitly specified metric and basis: << xAct`xTensor` << xAct`xCoba`(*Package*) Then comes an example of how to define and get all the quantities for Kerr metric. In your case you ...


2

I don't have a general approach but in a world where 19 and x^4+23 define our number field, a decomposition can be found by factoring the polynomial. InputForm[Factor[x^4+23,Modulus->19]] (* Out[3]//InputForm= (2 + 2*x + x^2)*(2 + 17*x + x^2) *) The upshot is that the ideal <19,x^4+23> in Z[x] is the ...


5

You need to use Remove[Global`Convert] instead of Remove[Convert] Convert is coloured red as a warning because both Units`Convert and Global`Convert exist, so when you simply type Convert one of the two has to be chosen, which might not be the one you wanted.


1

Messages defined for a symbol are stored in list of rules Messages[sym] similar to DownValues, UpValues etc. We can use this fact to create general message inheritance mechanism. Let's start with defining custom message on our own general symbol: ClearAll[general] general::myMessage = "text of general myMessage" As expected this message is stored in a ...


2

Adding directory to the beginning of the paclet search path One thing to note is that paclet search path is used only when getting files using a path with ordinary path separator. When getting packages using path with elements separated by context separator ` paclet search path is not used. To add a directory to beginning of paclet search path in ...


1

I'm afraid I don't know what realized covariance means. Perhaps the easiest solution is to use RLink and directly use the R implementation. Here are some links to the documentation to get you started. http://reference.wolfram.com/language/RLink/guide/RLink.html http://reference.wolfram.com/language/RLink/tutorial/UsingRLink.html



Top 50 recent answers are included