12
votes
2answers
1k views

Filtering and Replacing outliers

I have a set of data that measurements of temperature vs time (date). It is easy to realize when the sensor went wrong as one might see a blip on the data. How to teach to Mathematica to: 1) Detect ...
12
votes
4answers
476 views

“Strange” behavior of Rule

According to the Help lhs->rhs evaluates rhs immediately. How to understand the output of the following code? ClearAll@x; {1, 3.5} /. x_?IntegerQ -> {x} ...
11
votes
1answer
238 views

Segmentation fault on auto-complete

My front-end freezes as soon as I type more than two letters in a notebook. I think the error occurs, when the auto-complete feature kicks in. If Mathematica was started from a terminal, the following ...
11
votes
3answers
317 views

Why is (-1.)^2. a complex number

Why (-1.)^2. in Mathematica returns a complex number? It looks like in both C and Fortran it returns 1. Why does Mathematica behave differently than the other ...
11
votes
1answer
1k views

How to specify default style in Mathematica 9

In Mathematica 8, I can use GraphicsBoxOptions->{DefaultBaseStyle->{"Graphics", FontFamily -> "Helvetica", FontSize -> 14}} to specify the default font ...
11
votes
4answers
742 views

Why do some CountryData flags render at low resolution?

This question is related to data analysis introduced here Why do some flag images from the CountryData dataset render at very low resolution both in Front End and ...
11
votes
1answer
2k views

Where can I permanently modify $Path?

I've quite forgotten: what file does one modify in order to add directories to $Path globally? Specifically, I want to include ...
10
votes
1answer
982 views

How does Mma compute Confidence Intervals?

I am trying to understand how Mma computes the Confidence Intervals after a NonlinearModelFit. Consider the following example: ...
10
votes
7answers
1k views

How do I get rid of a “jump” in my plot?

How can I prevent plotting functions from "connecting" inside a plot points that should "wrap around" outside the plot? For example, how do I eliminate the horizontal lines running across the ...
10
votes
2answers
5k views

Performing a chi-square goodness of fit test

How would I perform a chi-square goodness of fit test? I have tried the following, where my data consists of the observed values whilst the data pair contains the correct values. Then I use the ...
9
votes
6answers
2k views

How to simplify a complicated Sum in terms of power Sums?

For example, I have: $a=\sum _{r=1}^n x_r \left(\left(\sum _{i=1}^n x_i-x_r\right){}^2-\sum _{i=1}^n x_i^2\right)$ ...
9
votes
3answers
5k views

Is there a simple way to plot complex numbers satisfying a given criteria

I think this should be straightforward, but I cannot seem to find a good source on how to do it after searching around, so I'm trying to sketch sets of complex numbers that meet a given for criteria. ...
8
votes
3answers
192 views

Complex result for Real vectors in VectorAngle

I was expecting a real angle using VectorAngle when passing real valued vectors, but I obtained a complex angle: ...
8
votes
4answers
569 views

Counting multiplications (complexity function)

I'm trying to count the number of times multiplication appears in an expression (for the purpose of constructing a ComplexityFunction that would help me simplify a terrible algebraic expression for ...
8
votes
2answers
171 views

Behavior of Inner depends on List dimensions?

Consider the following case: ...
8
votes
3answers
1k views

Checking if the roots of a function are real

I'm trying to determine if the roots of a function are real. How would you do that? (In particular I'm interested in verifying that the roots of LegendreP[6, x] ...
8
votes
1answer
417 views

Shortcut to insert CounterBox

Is there a shortcut to inserting a CounterBox as you type in text mode? I haven't yet made extensive use of them but I can foresee them in my near future and the ...
8
votes
3answers
2k views

Discrete Convolution

Ask to compute the convolution of 2 lists, I managed to do so, with what I feel is rather heavy : Let my 2 lists be : a = {1,2,3,4} b = {1,1,1,1,1,1}; The below function adds 0s on each part of ...
7
votes
0answers
86 views

NotebookWrite a Cell with WholeCellGroupOpener option [duplicate]

Why NotebookWrite[ EvaluationNotebook[], Cell["ZZ", "Section", WholeCellGroupOpener -> True] ] produces: ...
7
votes
3answers
226 views

Vector form using NDSolve

Michael E2 wrote a wonderful solution for my question. Now I am considering the system: $$ \begin{align*} x'&=x^2 y,\ x(0)=1\\ y'&=-x y^2,\ y(0)=1 \end{align*} $$ I am wondering how I can ...
7
votes
2answers
479 views

Click in a vector plot to plot several solutions of a system of differential equations

I am aware of the Locator button and I am aware of the Equation Trekker package, but they are not what I want to use. Here is what I specifically want to know how to do, if possible. Consider the ...
7
votes
4answers
421 views

Manipulate flickering and consuming lots of CPU

I am new to Mathematica and was experimenting with a simply problem of plotting a tangent to a curve and being able to move the point at which the tangent is drawn using ...
6
votes
1answer
420 views

Meshing the surface of a non-convex object

I would like to mesh the surface of a cloud of points that may not be completely convex, for example the points in this question. Mathematica does not provide triangulation of 3D points, but there is ...
6
votes
2answers
4k views

Need 4D plot (3D + color for function) [duplicate]

I have a function f(x,y,z) of three variables and some constants: ...
6
votes
8answers
649 views

Extracting matrix rows when one of its elements is part of a list (without a loop)

I have a matrix whose rows I want to extract based on whether the elements of one of its columns is a member of another vector (calling it the "comparison vector"). I would like to get better at ...
6
votes
2answers
712 views

Finding the intersection of two date lists

I've got two lists that look like this ...
6
votes
2answers
2k views

How to align rotated tick labels?

How can I align tick labels so the tick label text ends centered under the data point? Of Course it works fine with a rotation of 90 Degrees, but not with 45 or similar angles. I see an example of ...
6
votes
4answers
1k views

SIGSEGV error with 3D Plots

I originally asked this question here but didn't get a satisfactory answer. I am using Mathematica 8.0.1.0 on Ubuntu 11.10. I created a 3D plot from an ...
5
votes
3answers
621 views

ContourPlot and Colorfunction

I have the following code: ...
5
votes
2answers
876 views

ListContourPlot interpolation screws up on concave set of data

I want to create ListContourPlots for sets of Data (from a physics simulation) given as Triplets {x, y, f(x, y)}. Certain parameter regions in the x-y-plane are ...
5
votes
2answers
2k views

How do I draw lines perpendicular to contour lines on ListPlot3D?

I am plotting the voltage in a pool of water with two electrodes. I have contour lines on my graph at every volt, but I would like to show the electric field lines which are going to be ...
5
votes
3answers
438 views

Automatic Text Adjustment

Continuing the theme of minor interface annoyances, one of the unique features of Mathematica as a text editor is the automatic adjustment of text location as you type. This could be a bit ...
4
votes
3answers
4k views

How to remove ConditionalExpression from output

I need define the function with parameter so I could directly generate a power series expansion. The problem is that in some cases ConditionalExpression appears in output. Here is my code: ...
3
votes
3answers
171 views

Making large calculation results persistent

Very often, I need to do same calculations under different parameters for comparing the results. Every calculation may generate a large data set; for example, the calculation result of ...
3
votes
1answer
375 views

How to manipulate spoken text with Speak?

I need to vary the speed, pause, reverse and in general control aspects of the playback of Speak[] is this possible?
3
votes
1answer
552 views

How do I solve $1 - (1 - (A x)^2)^\frac{3}{2} - B(1 - \cos(x))= 0$?

Consider the equation $$ 1 - (1 - (A x)^2)^\frac{3}{2} - B(1 - \cos(x)) = 0 $$ where $A,B \in \mathbb{R}$ are constants. What is the analytic solution?
2
votes
1answer
269 views

Simplify expression to Abs

FullSimplify[Sqrt[1/(a^2 b^2)], Element[{a, b}, Reals]] gives Abs[1/(a b)] How do I simplify the following expression ...
23
votes
6answers
2k views

efficient way to count the number of zeros at the (right) end of a very large number

If I want to count the number of zeros at the (right) end of a large number, like $12345!$, I can use something like: Length[Last[Split[IntegerDigits[12345!]]]] ...
22
votes
2answers
895 views

How do I efficiently navigate the command line interface to Mathematica?

I would like to perfom such feats as cycling through previous commands, editing commands in place, etc. My expectation would be a readline-like interface, but this appears to not be the default.
21
votes
7answers
745 views

Elegant high precision `log1p`?

Sometimes it is hard to understand how numerical expressions are evaluated. I remember reading claims by Wolfram on how smart the Kernel is to evaluate expressions trees numerically by recognizing ...
16
votes
4answers
613 views

How to remove duplicates from set of machine precision 2D points?

I have a set of 2D points with machine precision coordinates. I need to remove all duplicates. Performance is important. This is the most obvious fast solution: ...
16
votes
6answers
3k views

X-Y scatter plot with coloring dependent on Z value [duplicate]

I have an array of $(x,y,z)$ triples (array dimensions: N x 3), from which I can make a 2D scatterplot of $(x,y)$ values: ...
13
votes
3answers
2k views

Combining Cos[ ] terms

A function that is the sum of two Cosine terms of the same frequency x[t_] := a1 Cos[w0 t + b1] + a2 Cos[w0 t + b2]; can be simplified to a single ...
13
votes
2answers
710 views

Factorizing polynomials over fields other than $\mathbb{C}$

I'd like to take a polynomial in $\mathbb{Z}_5[x]$ of the form $ax^2+bx+c$ and factor it into irreducible polynomials. For example: Input... x^2+4 Output... ...
13
votes
1answer
2k views

Kramers-Kronig in Mathematica

I am trying to calculate the change of the refractive index from the change of the absorption coefficient using the Kramers-Kronig relations, in Mathematica. ...
12
votes
1answer
1k views

Thickness of logarithmic tick marks

Bug introduced in 8 or earlier and persisting through 10.4 or later I'm trying to plot a graph wit a logarithmic y-axis. Since I'm exporting the graph to pdf and later printing it, I want to ...
12
votes
4answers
332 views

balanced Shortest[] and string-patterns

The pattern Shortest["A"~~__~~"B"] is oriented : It assumes the text is read from left to right and it takes the text between the first "A" and the next "B". Any ...
12
votes
5answers
1k views

define a function from a list

I would like to create a mapping from a list and I am wondering if there is a slick way of doing it. For example, consider the list ...
11
votes
6answers
389 views

Using MapIndexed only at certain elements of a list

MapIndexed is a very handy built-in function. Suppose that I have the following list, called list: ...
11
votes
5answers
2k views

How do you plot the same function with different options over different intervals?

Here is the motivation for my question. I want to plot Sin[x] over the interval 0 to 2 π, ...

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