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1d
comment Matrix multiplication for higher dimensional matrices
to clarify here, MatrixForm is a display function. it's used to show your results as a matrix, but is not used during calculations. you don't need to tell Mathematica "hey this is a matrix" because any rectangular list of lists is as good a matrix as you need. for example Det[{{a, 1}, {Graphics[Disk[]], d}}] will give an answer. this is a deliberate design feature. in particular, it means that all the functions you use for dealing with lists (such as Reverse) can also be used directly on matrices... and vice versa.
1d
comment Graphics3D artifact in Mathematica 10.1 64bit Home Edition - Windows 7?
could it be some kind of post-evaluation function that has attached itself to Graphics3D outputs that puts them in Pane? i don't remember what the commands are but the setting might be somewhere in AbsoluteOptions[EvaluationNotebook[]]. Actually, if this is the case it should be visible if you // FullForm the graphics3D output.
2d
comment How to create a thick spiral then extract the coordinates from the image?
Just as an addendum, ImageCrop[image] is useful for cutting back exactly after over-padding (such as with PlotRangePadding in this case).
2d
comment Graph, overlapping vertexlabels
This is probably the one failing of Mathematica's graphs presentation so far (poor handling of labels). Otherwise it's really pretty. Hopefully they improve labeling in the future. A couple things I would try here: Increasing/decreasing the ImageSize of the graph, as the labels don't scale in proportion to it. Removing the vertices altogether to get a cleaner graph, also fading down the edges a bit.
2d
comment Using function to transform a list
Here is a version of the code to show a few different things/tricks: Fcoord[{n_, s_}] := Module[{x, y}, {y, x} = 100*If[Divisible[n, 30], QuotientRemainder[n, 30] + {1, 0}, {Quotient[n, 30], 30}]; s /. { "I" -> {x, y}, "II" -> {-x, y}, "III" -> {-x, -y}, "IV" -> {x, -y}}]; Fcoord /@ {{242, "I"}, {56, "IV"}} Note that Mathematica has functions for a bunch of stuff, even for things you would normally think are too specialized.
2d
comment Using function to transform a list
oh i see. it's because function parameters are "literal" pattern replacements (they aren't really variables), so when you type coord[[1]] = x inside, the system sees it as {300,II} = x when it is applied. there's ways around this, but i would recommend using Map as you are attempting to. Map isn't designed to modify the original list, it always gives you a completely new list. lots of $$ goes into making this inefficient-sounding thing efficient, so generally you shouldn't worry about performance with something as basic as Map. Also take a look at functions such as NestList.
2d
comment Using function to transform a list
on first glance, you are using = (assignment) where you mean == (equality) ?. by the way it's good that you're trying to go with Mathematica's style. it may take a while, but it will pay off.
2d
revised Mathematica's ViewPoint versus MATLAB's View command
deleted 71 characters in body
2d
comment Curvature Application
@nikie by chance have you written any books? if you wrote an "image/data processing/analysis in mathematica" book, i'd buy it (as long as it was not more than $85).
Jul
2
answered String matching balanced pairs of braces
Jul
1
comment How to create a thick spiral then extract the coordinates from the image?
@Solarmew no problemos. i'm guessing Binarize is choosing a different background based on some threshold, or something like that. Just use ColorNegate to get the polarity you need. For the cropping issue you could adjust the PlotRange but the easiest is to set a padding: PlotRangePadding -> 3. By the way, you can do something like ComposeList[{Binarize, ColorNegate, ImageData, MatrixPlot}, plot] // Column to follow these kinds of sequential transformations.
Jul
1
revised How to create a thick spiral then extract the coordinates from the image?
added 2 characters in body
Jul
1
answered How to create a thick spiral then extract the coordinates from the image?
Jul
1
comment How to create a thick spiral then extract the coordinates from the image?
do you mean just PolarPlot[theta/2 Pi, {theta, 0, 2 Pi}, PlotStyle -> {AbsoluteThickness[8], CapForm["Round"]}, Axes -> None] // Binarize // ImageData // MatrixPlot ? by setting large ImageSize you can increase the resolution. you can also use Position[imagedata,1] and ImageValuePositions[im,1] for coordinates
Jun
27
comment Drawing a ladder graph with Line and Table/Array
by the way, FullForm[Normal[Show[GridGraph[{8, 2}]]]]. interestingly, by converting to graphics with either Show or FullGraphics, you can move vertices around and the edges stay connected.
Jun
27
answered What is the role of _ in this expression?
Jun
22
awarded  Good Answer
Jun
22
revised Creating a simulation of our Solar System
deleted 178 characters in body
Jun
22
revised Creating a simulation of our Solar System
updated the program
Jun
20
revised Mathematica equivalent to Python long raw strings? handling escape characters in packages
deleted 97 characters in body