# Tag Info

### Trace shows Linux has worse error than Windows in 1/(-1.)^1.2

This made me curious. I work under macos on Apple Silicon. I get these results: ...
Accepted

### How to use Slater Type Orbitals as a basis functions in matrix method correctly?

Your orbitals are not orthogonal to each other: here I've normalized them with an explicit formula (using FindSequenceFunction to discover it): ...
• 41k
Accepted

### How can I solve a three-dimensional Gross-Pitaevskii equation?

After proper normalization we have ...
• 38.5k

### Solving PDE with Dirichlet, Neumann and Boundary conditions

4 issues here, 2 are simple mistakes, 2 are not. Though it happens not to cause problem in this case, your understanding for syntax of Piecewise is wrong, please ...
• 59.4k
Accepted

...
• 42.9k

### Why two the same integrals give different values?

Evaluating high-order polynomials is numerically unstable. Example: exact evaluation followed by numericalization is stable, Psi[7, 87] // N (* -0.0271578 *) ...
• 41k
Accepted

### Trace shows Linux has worse error than Windows in 1/(-1.)^1.2

I'm not sure I understand the problem, despite attempts get clarification. So far I'm not sure there is much more to this than to the following, this-is-school-math, behavior: ...
• 226k
Accepted

### Poorly behaved ContourPlot

Increase the PlotPoints (it takes sometime to compute!): ...
• 1,513

### Solving PDE with Dirichlet, Neumann and Boundary conditions

modified Thanks to @xzczd for the helpful discussion Here my simplified version without ghost layer and mapping: The ...
• 42.9k

### NDSolve with parametric endpoint

Integrating toward b[eta] = y'[eta] = 0 is challenging, because b[eta] occurs in the denominator of the first ODE. So, it ...
• 59.7k

...
• 139k

### Calculating the angle between vectors returns small complex number instead of zero

First note, the expression: Transpose[{{10}, {12}, {4}}] . {{2.5}, {3}, {1}} does not make sense. You are trying to mimic column and row vectors, but MMA does not ...
• 37.4k

### How to numerically solve a differential equation which has integration in it?

Some progress can be made as follows. First, rescale X by 10^7 to avoid large values of X (...
• 59.7k

Maybe this?: ...
• 226k

### Complex result for real vectors in VectorAngle

This is to note that at some point, this bug in VectorAngle has been fixed in or before V13.2: ...
• 226k

### Calculating the angle between vectors returns small complex number instead of zero

The numerical problems are two-fold and are independent of syntax and the OP's use of column matrices as vectors. The most serious problem is that round-off error leads to a range of  -1-\delta \le {...
• 226k
Accepted

### Improving quality of plot with bad numeric performance

Don't use machine precision. Specify a WorkingPrecision to use arbitrary-precision. ...
• 139k

### Can Print no longer access certain values during evaluation?

It's not Print but FindRoot that has changed its behavior. FindRoot now evaluates its ...
• 226k

### CPU time in iteration process

How I set the CPU time or where I can check the CPU time for method One way is to use TimeUsed[] and at the end subtract the times. Something like this ...
• 127k
1 vote

### Calculating the angle between vectors returns small complex number instead of zero

This problem does not occur when normalizing the vectors with Normalize: ...
• 41k
1 vote

### Calculating the angle between vectors returns small complex number instead of zero

This is not an answer, but too big for a comment. What you found is very annoying, and I can provide no solution. But maybe the following code is of some help. ...
• 1,833
1 vote

### How to numerically solve a differential equation which has integration in it?

Perhaps StreamPlothelps to understand the problem little bit better ...
• 42.9k
1 vote

### How to numerically solve a differential equation which has integration in it?

Not an answer, perhaps a starting point... You could try to find an iterative solution (Picard iteration) using NestList starting with ...
• 42.9k

Only top scored, non community-wiki answers of a minimum length are eligible