# User Portlet

Neil Singer
Discussions
Your NDSolve code seems to work fine. Why do you think there is a problem with the NDSolve solution? I don't understand why you want to implement your own integration when Mathematica already has most techniques built in if you set the Method...
Jaime, I would report this as a bug -- sometimes it works and sometimes it does not. It must depend on the data. If you avoid the text file, it works at any size (I tried up to 10,000,000). Use d1 = RandomVariate[NormalDistribution[0, 1],...
Jérôme, > However, I find strange that Mathematica is not able to compute properly a simple division like 24.9 / 6 without using the Rationalize function. My calculator do it without any probleme... Mathematica does do 24.9/ 6 exactly like your...
You can also just use ComplexExpand because it assumes all variables are real unless specified as complex: ComplexExpand[Abs[k1*I + 1]] Mariusz's post is better if there are further simplifications from the fact that k is Positive (which in...
In addition to Rohit's suggestion, I would add ContinuousAction -> False to the Manipulate so it only updates when you release on a new value and does not try to continuously update (which it really can't do well). Regards, Neil
Mor, **Motor Modeling** The only reason I mentioned the motor issue is that you had a resistance and inductance but eliminated them (from a dynamics point of view) by forcing current. With the new model, your resistance and inductance now have...
Nils, SeriesCoefficient[] works properly on the expression without distributing the term: In[1]:= exp = Series[2^(2 k)*(Sinh[x/2])^(2 k), {x, 0, 5}]; Table[SeriesCoefficient[exp, n], {n, 1, 5}] Out[1]= {0, 1/12 k x^(2 k), 0,...
Mariusz, I like your approach of symmetrically jumping over the singularity (fix the q’[x] to the absolute value and restart from there). Its clever. I’m curious, What would be the physical meaning of that solution? Is it connected to the first...
You need to post code and a better description of exactly what you want for us to be more helpful, but I would look at the help for Integrate and search for "CoordinateChartData". The example will show you how to get the VolumeFactor for your...
One of the most important parts of the documentation in Mathematica is the "See Also" (either the drop down menu at the top of the help window or the list at the bottom). If you go to a function that is close, you will likely find what you need...