7
votes
1answer
87 views

Bug in GeneratingFunction?

According to the documentation GeneratingFunction[a[n],n,x]==Sum[a[n]x^n,{n,0,Infinity}] However, for $a_n=1/(n+2)$ I obtain ...
2
votes
0answers
75 views

Det and MatrixRank freezes on SparseArray with nonzero default value

Why does the following simple code never come to an end (at least with version 8) n = 5; mat = SparseArray[{i_, i_} -> 1, {n, n}, -1/(n - 1)]; MatrixRank[mat] ...
13
votes
2answers
366 views

Problem importing URL with Greek characters

I'm considering buying a car. So I thought why not make a web-crawler in Mathematica to pile-up car data? Brilliant idea. Then I found this Greek website, gocar.gr, which just so happens to have all ...
8
votes
2answers
416 views

Problem with ContourPlot3D

The following line works fine: ...
3
votes
0answers
92 views

An recurrence equation that can be solved in version 7 but not in version 8

A friend of mine showed me this code sample: RSolve[{a[n] == a[n - 5] + 1, Sequence @@ Table[a[i] == 1, {i, 5}]}, a[n], n] // Timing It's solved by version 7 in ...
2
votes
1answer
146 views

Version 7 and 8, different behavior of NSolve. Is it reproducible?

I noticed the following difference, and I wonder if it's a problem of my system or the results difference is actually due to the two different versions ...
11
votes
2answers
429 views

backward compatibility

When producing or enhancing code, it is tempting to use recent new primitives of Mathematica introduced in version 7 and 8, but for library code or in preparation or future version change in ...
4
votes
0answers
227 views

NullSpace[_, Method->“OneStepRowReduction”] is sometimes wrong; how can I work out when this happens?

(This is on MMA 7.0.1.0 on OS X) I've just found a large matrix m for which NullSpace[m] and ...