3
votes
1answer
69 views

Bug with LinearProgramming on Integers?

With Mathematica 7: LinearProgramming[{1, 1}, {{0, 0}, {1, 1}}, {1, 1}, Automatic, Integers] gives wrong result {0,1}. But ...
20
votes
1answer
216 views

M9 performance regression for Fold?

I noticed an over 10x performance drop on Mathematica v9.0.1 (as Oleksandr R. commented, also v8) compared with v7.01 for this code: ...
4
votes
1answer
92 views

Animated matrix will not work?

I want to export a list of matrices as a gif so that they will appear one after another 2 seconds apart. Ive tried the following but when I open it up it only does the first two matrices, I have 10 ...
4
votes
0answers
64 views

Error with String patterns producing Removed[“$$Failure”]

While working on How to capitalize the first letter of each word in a string and trying to understand why certain characters were not considered letters I tried this: ...
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
370 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 ...
6
votes
0answers
138 views

Mathematica 7: “LessEqual::nord:” error when using NMinimize on a real function

I encounter a problem (Mathematica 7) similar to Strategies to avoid LessEqual::nord in NMinimize? but the advised strategies don't work for me. Also, I get different results with different ...
8
votes
2answers
420 views

Problem with ContourPlot3D

The following line works fine: ...
7
votes
3answers
416 views

Plotting a 3D list causes kernel to crash if x and y axes have vastly different scales

I have access to two versions of Mathematica, version 7.0.1 on Linux and version 8 on Windows. When I try the following two lines on version 7, the kernel quits when it tries to plot. In version 8 ...
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
0answers
355 views

Simple contour integral with a parameter gone wrong

I run into the following problem, I tried to evaluate a very simple integral: Assuming[ a > 0 , Integrate[Sin[a*s]/(s - I)^2, {s, -Infinity, Infinity}]] ...
4
votes
0answers
230 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 ...
7
votes
4answers
294 views

Unexpected behavior from GatherBy in version 7

I have come across what appears to be a bug in GatherBy. It appears similar to the problem of using Table[Random[], {1000}] in ...