6,144 reputation
1143
bio website
location
age
visits member for 2 years, 5 months
seen 2 hours ago

Jan
16
comment How to get a rule for, e.g., (x + y) to apply to (-x - y), etc.?
Use FullForm[x + y] and FullForm[-x - y] to see how those two expressions are different (or TreeForm if you are feeling daring). ReplaceAll is a dumb function that is not going to transform your expression for you. It may not be friendly, but it is reliable. In general, as Kuba has suggested, it's better to replace atomic elements.
Dec
10
comment calculating a sequence of functions using iteration
Actually I'm not sure how one would effectively memoise this. How do you cope with the conditions on the argument that isn't memoised?
Nov
20
comment 3D Plot of .txt File of the Surface Plotting Variety
I probably wasn't clear in the answer. Import["C:\\yourfile.dat", "Table"] will read the file directly. I just used ImportString as a toy example.
Nov
18
comment Fitting a function
You could use a rule fit /. m_ t + c_ :> m or pick out the right part fit[[2, 1]]
Oct
17
comment Too much whitespace in a GraphicsGrid containing Legended Plots
You could try Grid instead of GraphicsGrid.
Oct
17
comment Newton-Raphson Method and the Van der Waal Equation Coding question
Looks like you actually want a root this time instead of the minimum. Change FindMinimum back to FindRoot. Also don't forget to adjust your PlotRange.
Oct
17
comment Newton-Raphson Method and the Van der Waal Equation Coding question
Starting conditions were found by trial and error: minimise with a starting value function, plot the results, make up a new function that approximates the good bits of the plot, repeat. See the edit for a better way to do it.
Oct
15
comment Customizing & finding intersection points in polar plot
That's why I'd like to know exactly what the theorem is. As far as I can tell, the curve does not go through equally spaced points at those angles (aside from my ability to count to eight).
Oct
14
comment Customizing & finding intersection points in polar plot
That's not a golden spiral. This might be PolarPlot[GoldenRatio^(2 n/\[Pi]), {n, 0, 2 \[Pi]}]. Can you quote or link to the theorem?
Oct
10
comment How can I speed up my numerical integration?
And should x0 be -50 or 10^-50?
Oct
9
comment How can I speed up my numerical integration?
What's x2? Also, your function f doesn't seem to use xe?
Sep
5
comment Text as plot axes values
What's the deal with Europium?
Jul
17
comment Picking numbers within a list with an interval of 60
You might need to explain a bit more clearly. For example, what's wrong with {5, 14} as one of your sublists? Posting your existing code always helps too. Split and Gather are useful functions for this type of problem.
Jul
16
comment Problem with Looping/Recurrence - Null Results
"Unless an explicit Return is used, the value returned by Do is Null."... and you are printing that Null. Just evaluate list after the loop and see what it is.
Jun
26
comment Why doesn't FindRoot work correctly?
It's finding a root, which is all it is asked to do. Starting a bit closer might give the root that you want. Try changing your .5 to x.1.
Jun
20
comment Efficient Generation of Subgraphs (or, unfriend a friend a day)
With 10 people, they each have a choice of 9 unfriendings, giving $9^{10}$ possibilities. The next day there is probably still 10 people with 8 choices, so the total possibilities so far is $9^{10} 8^{10}$. This gets very big, very fast. I don't think you are going to brute force it.
Jun
18
comment StringReplace except some pattern
@HyperGroups Indeed. Have edited to fix.
Jun
5
comment Maintaining map dimensions after using Colorize
Why not {RGBColor[0, 0.33, 0.643], Rectangle[{-6, 41}, {-0.77, 51.5}], White, Rectangle[{-0.77, 41}, {4.47, 51.5}], RGBColor[0.98, 0.235, 0.196], Rectangle[{4.47, 41}, {9.7, 51.5}]}?
May
16
comment How to generate characters by a function which works like the Esc + a + ESC
@Mr.Wizard You're welcome to improve it. It's definitely a bit rough around the edges at the moment.
May
16
comment Generating partitions of a set with a specified size of the parts
Isn't there just one result, given by Partition[myList, 2]?