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17h
comment Undocumented form for `Extract`
New in 3 | Last modified in 8 | Documentation last modified in 5 :-)
18h
comment Create new file, based on 500 articles
@MichielvanMens, sorry, I missed the point of the question. See my edit.
1d
comment how to find find a matrix by the characteristic vlaues and vectors
Is this a question about mathematics, or the software Mathematica? This site is for the latter.
1d
comment Map structure of irregular list, Flatten then reconstruct list using structure
If you attempt to reconstruct the non-tensor object inside Compile it will generate a callback to the main evaluator.
2d
comment Enter exact rational numbers easily with decimal notation
How about $Pre = # /. r_Real :> RuleCondition[Round[r, 10^-Ceiling@Precision@r]] &
2d
comment Resume/continue interrupted evaluation
Does pressing F5 work?
2d
comment Plot Notes present in sound sample
The numbers in SampledSoundList are samples of the wave amplitude. You need to do some processing to convert this data to a time-frequency representation. One way is to split the data into chunks (partitions) and compute the discrete Fourier transform of each chunk, which is what SpectrogramArray does. The second argument is the length of each partition, i.e. the number of samples it contains.
2d
comment How to manually set z-axis values in a 3d plot?
@LoryLory, MathWorld is quite good for that kind of thing, there is also Wikipedia of course.
Apr
14
comment How to manually set z-axis values in a 3d plot?
Why not just plot the ellipsoid? SphericalPlot3D[h r/Sqrt[r^2 Cos[θ]^2 + h^2 Sin[θ]^2], {θ, 0, π/2}, {ϕ, 0, 2 π}]
Apr
14
comment Errors of machine precision
The message means that Mathematica has tried to evaluate the numerical value of Log[Abs[4 + 4 Exp[-2 I Pi/3] + 4 Exp[2 I Pi/3]]] and in doing so has reached its internal precision limit (determined by $MaxExtraPrecision).
Apr
14
comment Plot Notes present in sound sample
Look at SpectrogramArray, especially the "Neat Example"
Apr
13
comment Transform elements in list from form {x_} to form {x_, 0}
Dot is the winner here, with v9 on Windows. Closest I can get to it is the rather ugly Transpose[Join[Transpose[a, {2, 3, 1}], ConstantArray[0., RotateRight@Dimensions@a]], {3, 1, 2}] which takes about 20% longer.
Apr
13
comment Programming paradigm change
The new one is very clever. I don't think I've ever seen non-strings on the rhs of StringReplace rules. Nice...
Apr
12
comment Partitioning an image based on features
@Sektor, Classify is a new function in v10
Apr
11
comment Programming paradigm change
@Mr.Wizard, I decided the use of spaces was inconsistent in the original string so didn't worry about it ;-)
Apr
11
comment Generate array of every $n^{th}$ integer between two bounds
@Öskå, I've voted to close as RTFM but if you'd rather keep it open please feel free to combine your comment and mine into an answer.
Apr
11
comment Generate array of every $n^{th}$ integer between two bounds
Array does not take an iteration variable. Use it like Array[1926 + 4 # &, 22] or alternatively use Table[1926 + 4 m, {m, 22}]
Apr
10
comment How to solve correctly inside a DO loop and then plot
Why not use ContourPlot[V[x, 0, z0] == E0, {x, -2, 2}, {z0, 0, 0.6}]
Apr
9
comment Capture an image by non-default device
Does Block[{$DefaultImagingDevice = $ImagingDevices[[x]]]}, code here] work? Sorry, got no imaging devices to test with.
Apr
9
comment Import and Extract Frames from Video files in Mathematica
Import can import .avi and .mov video files. Note that it relies on Apple QuickTime for decoding, so if you don't have QuickTime installed you are restricted to uncompressed avi. I generally use a third party application to extract frames from the video and just import the image files into Mathematica. These questions might be of interest: mathematica.stackexchange.com/q/161/862 and mathematica.stackexchange.com/q/18335/862