Edit: Clarification: I think we should start closing questions which are obviously copied verbatim from a homework assignment and which consist of no other text. Questions about homework with other text, e.g. "I tried X and it doesn't seem to work," are fine.
Many people are asking 1. how we sh...
@Szabolcs I don't know what's state-of-the-art these days, but the method I'm familiar with is Lanczos. If you don't need eigenvectors, then you can use this to tridiagonalize a sparse matrix.
@halirutan Okay, I'll do that. Perhaps though it would be better to find more than one change before bothering someone with it. Have you noticed anything else that would be easy to fix/extend?
Hello guys! I was looking into a way of deleting a certain element of all sublists in a list. I was looking into `Delete[mylist,{All,4}]`, but `All` does not work in this case.
The built-in function "Drop" can delete a Matrix's row and column.
Typical syntax for "Drop" is as follows:
Drop[list,seq1,seq2...]
But what if I want to drop a matrix in a way that the indices of the columns to be deleted is not a well ordered sequence?
For example the matrix is 10x10, And ...
I am trying to delete both a matrix in mathematica. An inelegant way of doing it is as I do below, i.e specifying it in a new matrix as
S = Table[
Ss[[If[i < t, i, i + 1]]][[If[j < t, j, j + 1]]], {i, q}, {j, q}];
where the goal is to eliminate row and column t.
Indeed delete a line...
@Sosi I notice that in a comment Daniel proposes Drop[mat, None, {colnum}]. I'm not sure if that performs any differently from using 0 but it might be more clear.
Part directly supports lists of indices when slicing arrays. The following definitions exploit that:
takeOperator[a_?MatrixQ, rows_List, cols_List] :=
a[[rows, cols]]
dropOperator[a_?MatrixQ, rows_List, cols_List] :=
a[[##]]& @@ complementaryIndices[a, rows, cols]
complementaryIndices[a_?M...
I dont know, but the first thing it would come to my mind would be to analyse it as a string or something like that.. Not the best solution, that's for sure..
@halirutan Ah yeah, I noticed that same question! Yep, I think more and more, people come online hoping to have someone else doing their own work for them
Contrast "waaa I entered (blah) into Mathematica and it doesn't work!!!!1!" with "I was trying out (blah), and I did not get what I want. I checked the documentation, but I couldn't find anything..."
@halirutan At the very least, that poster isn't subbu. A schmuck of a different sort, that one.
Oh, @halirutan: you told me about an article you guys were working on that used the periodic interpolation. If it's not too much to ask, can you send me a copy when you guys are done?
@J.M. that happened to me quite a few times ever since I discovered MMa.SE. But then again, sometimes (like in here: chat.stackexchange.com/transcript/message/9208602#9208602) I need to come here and ask these sooo simple questions that make me feel bad about even asking them :P but in the end there is always someone nice around that is patient enough to help
@Szabolcs There's a polishing procedure for getting the tridiagonal you'd have gotten from Householder, if memory serves.
But, you're right, the primary use for this was due to the fact that the tridiagonals that come out in early iterations already have a spectrum similar to the original's.
My name is Mohammad Rizvi, I am an Author Relationship Executive at Packt Publishing. We specialize in publishing IT related books, e-books, and articles that have been written by experts in the field.
Packt is planning to publish a book on Mathematica , titled Mathematica Data Visualization .
Given your experience with Mathematica, I was wondering whether you would be interested in authoring this book.
Please let me know if you would like to know more about the book.
Awaiting Reply,
I would never buy a book from a publishing company daring to select me as an author
I got a 30 day trial version of Mathematica 9.0 and was quite annoyed to see that Export is not available in the 30 day version! Does anyone know what else is perhaps unavailable? I got ver. 9.0 since ArrayPlotsMatrixPlots with PlotLegends->... has better one-to-one data correlation and now I am rather miffed! :(
@J.M. Sigh. Rather unfortunate. I had recently moved away to python and wanted to relapse :P to mathematica! I guess I will have to wait until I am rich enough to afford a full, un-restrained Mathematica 9.0 license.... :(
I am trying to delete both a matrix in mathematica. An inelegant way of doing it is as I do below, i.e specifying it in a new matrix as
S = Table[
Ss[[If[i < t, i, i + 1]]][[If[j < t, j, j + 1]]], {i, q}, {j, q}];
where the goal is to eliminate row and column t.
Indeed delete a line...
Part directly supports lists of indices when slicing arrays. The following definitions exploit that:
takeOperator[a_?MatrixQ, rows_List, cols_List] :=
a[[rows, cols]]
dropOperator[a_?MatrixQ, rows_List, cols_List] :=
a[[##]]& @@ complementaryIndices[a, rows, cols]
complementaryIndices[a_?M...
I want to plot 2 function on one plot.for example x^2 at [-1,3], x^5 at [0,4]
