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| bio | website | quantdec.com |
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| location | ||
| age | ||
| visits | member for | 1 year, 5 months |
| seen | Jun 5 at 22:21 | |
| stats | profile views | 967 |
Consultant (environmental stats a specialty) and teacher.
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May 3 |
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Calculate variance of random walk? This isn't really a question about Mathematica; it's a math-stat question. The answer is that the variance of $X_t$ is the sum of the variances of the $Z_i$ and the variance of $Z_i$ equals $p(1-p)(2-2k)^2$. |
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May 3 |
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Checking if an expression is equal to zero possible duplicate of How to check if a 3D point is in a planar polygon?: the solution to that one requires an initial check that answers the present question. |
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May 3 |
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ode with boundary value problem does not work I don't see any "boundary value problem" here: this is a second order nonlinear ODE for $\lambda$. There are several critical typographical errors in the Mathematica code, not least of which is the lack of any appearance of the second derivative of the unknown function. I have voted to close this question as too localized: it does not appear to be a Mathematica issue in any way. |
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May 3 |
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ode with boundary value problem does not work What value does h0 have? Note, too, that the initial conditions are overdetermined: specifying one (and not three) is enough. |
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May 2 |
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Problem using replace to simplify logarithms 70 threads are listed in the search for simplify+log. Many of them answer this question in various ways. |
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May 2 |
answered | Representing a Stencil of a Finite Difference Operator with Mathematica's Graphics3D |
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May 2 |
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Assuming monotonicity and concavity Could you clarify what you mean by "evaluate"? Have a, u[10], and q been given definite real values or do you want to find combinations of them for which the inequality might be true for some phi? |
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May 2 |
reviewed | Leave Closed Adapting NDSolve to circumvent NDSolve::bdord: error for 1-D Euler Equations |
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May 1 |
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PolynomialRemainder memory Could you amplify this answer and show how your suggestion would work in Mathematica? It's especially puzzling that the reference you give makes no mention at all of polynomials. |
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May 1 |
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Breaking up data and finding independence thils, it now sounds like you mean statistical independence, not linear independence. The two are entirely different things! Also, if you want something "convenient for later manipulations," you really ought to specify what procedures you have in mind--please don't make us guess. Edit your question to clarify what you need. |
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May 1 |
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PolynomialRemainder memoryPolynomialMod[1 + x^267910657, {1 + x + x^20 + x^32, 2}] |
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May 1 |
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Finding the common areas of two contourplots Although some people have answered, which indicates they think they know what you have in mind, this question has some striking ambiguities. Perhaps if you were to explain what you mean by "parameter spaces" and how the "common areas" are defined you might get some responses that are closer to what you're looking for. For instance, is an "area" a geometric region, a rectangular extent, or is it perhaps a number representing its area? Are the "parameter spaces" the ranges of X and Y values shown in your plot or are they something else that needs to be derived from your input? |
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May 1 |
reviewed | Close Help with 1-dimensional random walk |
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May 1 |
reviewed | Close Function Nodal2`NodalNetwork is not evaluating |
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Apr 30 |
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Statistical analysis of data-list with recurring x-values I think it's this: you're trying to do an ANOVA at the same time you're estimating different variances in each cell. You will get stuck in any cell with just one value. It might sort of work but has no theoretical justification. (Some could be supplied--the easiest way is through a maximum likelihood model (which, btw, will never include an adjustment for bias!)--but it would cause your formula to change a little.) The linear fit on the raw data effectively combines all residuals into one overall estimate of variance: that suggests using $n_i$ as the weights; forget the variances. |
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Apr 30 |
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Mathematica plots a discontinuity in piecewise function that does not exist possible duplicate of Plot showing discontinuity where it shouldn't. Also a duplicate of mathematica.stackexchange.com/questions/19877/…. For more information, do a search. |
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Apr 30 |
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Statistical analysis of data-list with recurring x-values I don't think it will be biased--I believe you're thinking of something akin to ANOVA with the x-values as categories. In your answer you are treating those x-values as numbers. Intuitively, if you tried to apply the Bessel correction to your variance estimates you couldn't even get a variance for any x-value that isn't replicated. Obviously that's not right: for fitting the straight line it's possible to include single values along with averages of two or more. (It's hard to estimate the variances of non-replicated values, though!) (+1 for the edits, BTW.) |
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Apr 30 |
awarded | Good Answer |
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Apr 30 |
reviewed | Close How to monitor the progress of Importing files? |
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Apr 30 |
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Statistical analysis of data-list with recurring x-values There are multiple problems with this fitting approach. First, the weights should be inversely proportional to the variances of the means rather than of the data themselves. (You need to divide the variances by the counts.) This means the error bars at the beginning are incorrect, too. Second, the variances need to be computed as population variances rather than the sample estimates: otherwise, you will be in real trouble if an x-value is not repeated! Third, why bother when the result ought to be the same as if the fit were made with the original data? |
