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1d
comment Algebra problem
pretty tough to work a problem without knowing exactly what it means. whats the "?"?
2d
comment Finding “Maxima” and “Minima” on a B-Spline
I agree its odd there isn't a built in way to do this. For this case by the way you could as well do Table[gpy[t], {t, 0, 1,.01}] in place of the Cases[Plot..][[1,1]] because the function is nice enough we dont really need the adaptive sampling that comes from using Plot
2d
comment Surface area of intersecting spheres
for comparison Method -> "LocalAdaptive" crunches away for 2-3 minutes (without errors) and gives 1.69185 (1.8million evaluations). I'd be inclined to thinks that's more accurate, of course without an analytic solution thats just a hunch.
2d
comment Finding “Maxima” and “Minima” on a B-Spline
Just using g instead of g' should do what you want (at least in this case with only one local min and max )
Apr
20
comment Surface area of intersecting spheres
the best approach most likely involves generating a triangular surface mesh (I don't think any of NIntegrates methods will do that unfortunately.) Thats a bit involved to work up as an answer, but if you do a search there are a few meshing questions on this site.
Apr
19
comment Surface area of intersecting spheres
are the 'n` spheres themselves potentially self intersecting? If not this can readily be done analytically.
Apr
19
comment Find lengths of contours in a ContourPlot
start by doing Cases[ContourPlot[...],Line[pts_]:>List[pts],Infinity]. Use ListPlot to verify the extracted lists are your contours. It is then a simple matter to find the length of the line.
Apr
18
comment How to get integer/rational and real eigenvectors to be the same?
something like (# Sign[ Total@ # ] )&/@ eigenvectors should do.
Apr
18
comment How to get integer/rational and real eigenvectors to be the same?
the sign change is not explicitly mentioned in the link, but it is essentially the same issue. You can "fix" by choosing a convention that suits you such as multiplying by the Sign of the largest magnitude component. Look at the answer here math.stackexchange.com/questions/235396/eigenvalues-are-unique
Apr
17
comment Generate a list of values with equal number of each value
your formula is right but not the number: 32 (32!/(16!)^2) == 19234572480 (off by 1/2 .. )
Apr
17
comment complicated Numerical Integration, FEM application
mathematica.stackexchange.com/questions/34657/…
Apr
17
comment complicated Numerical Integration, FEM application
the other thing you need to take that inner integral and turn it into a function that takes only numeric arguments (eq inner[x2_?NumericQ, y2_?NumericQ, xz_?NumericQ, yz_?NumericQ] := NIntegrate[...] . Probably add ?NumericQ to the arguments of t and B2 as well
Apr
17
comment complicated Numerical Integration, FEM application
your definition trans:= does not create a function that takes four arguments. You should do trans[x1_,y1_..] (Its not immediately obvious what args should be)
Apr
17
comment How to get more accurate orthonormal eigenvectors?
you are asking for output that is higher precision than the input
Apr
17
comment draw graphics in cycle
lots of basic syntax errors, where to begin?
Apr
16
comment Solving nonlinear system by newton method
This question appears to be off-topic because it is not about mathematica
Apr
16
comment Recover data points from RGBColor of known ColorScheme
The issue is that color scheme has a region of a constant channel (Red==0 for z<1/4), so Solve fails.
Apr
16
comment Recover data points from RGBColor of known ColorScheme
Nice +1. Just to make some extra work it doesn't work quite right with some other color schemes eg. ColorData["AvocadoColors"] (random choice.). I'm guessing it needs just a little tweak to make more robust.
Apr
16
comment Randomly selecting and reinserting a subset of elements in a list
nit picking i think you need to add 1 to the random range or you'll never insert at the end
Apr
16
comment How can I use a For loop in a recursive function?
your loop doesnt get past k=0 since it immediately hits Return