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Wolfram Blog
Wolfram Blog
2:59 PM
Wolfram Blog: Reliability Mathematics in Mathematica
posted on September 30, 2013 by Johan Rhodin

What is the cost of extending a warranty for a car? I’d be interested to know, since my car broke down just past the 100,000 mile marker on a road trip through America. With Mathematica 9 comes complete functionality for reliability analysis that can help us analyze systems like cars. I thought it might be [...]

 
rm -rf
rm -rf
3:57 PM
@halirutan Hehe, check this out:
1
Q: Plot 3D vector that is a function of one variable

Ben7005I have a function, r[t], which is a piecewise function that generates a 3D vector. It looks like this: r[t_] = Piecewise[{{{5 t, 0, 3 (1 + Cos[t])}, 0 <= t <= π}, {{5 Cos[t - 3 π/2] + 5*π, 5 Sin[t - 3 π/2] + 5, 0}, π < t <= 2 π}, {{5*π + 3*Cos[t - 3 π/2], 2*5 - 3 + 3*Sin[t - 3 π/2], 1/(2 π)...

plotting vector
the exact same piecewise function asked about a year ago!
This certainly looks like a homework and the professor is just recycling the same old question :P
 
Calle
Calle
4:16 PM
Can't find the particular problem but I suspect it's this class. amath.colorado.edu/content/…
 
halirutan
halirutan
4:27 PM
@rm-rf And not to forget this here..
 
Calle
Calle
Yes, it is that class. @halirutan here's the problem that you wanted (probably not seriously lol) to solve once and for all: amath.colorado.edu/sites/default/files/2013/09/1121202723/…
Also, I would make a great PI.
 
halirutan
halirutan
@Calle Pretty strange that the parametric function is not given explicitly there and that all those guys came up with the same syntax.
 
rm -rf
rm -rf
pretty much copy pasted
 
halirutan
halirutan
@rm-rf Ahh there you go..
Maybe I should write the prof a short notice.
 
rm -rf
rm -rf
Please feel free to do so
@halirutan I hope you got the message, if not, you should be able to see the history
@halirutan hehe, or we could just solve the entire homework set and project, answer it here and send an email to the class mailing list :P
 
halirutan
halirutan
4:56 PM
@rm-rf Sorry, I only see (removed) ;-)
Was eating.
@rm-rf Actually, I proposed exactly this yesterday. By providing a complete Q&A we could close all other things as duplicate.
I think this is a pretty neat homework project and it is really embarrassing that the students are here to ask even the most simple questions about it. I'm sure most of this stuff can be found in their lecture notes :-(
 
rm -rf
rm -rf
5:28 PM
@halirutan If you click the down arrow to the left of the message (hover), do you see a "history" link? I thought room owners could see the history... maybe I was mistaken.
@halirutan Yes, their notes do seem sufficient to cover the questions being asked here... It's a shame, but then, I too was once an undergrad and I know fully well how much attention is being devoted to the lectures... :D
 
halirutan
halirutan
@rm-rf No, you are right.
I didn't know that I have so much god-like power.
 
rm -rf
rm -rf
@halirutan Hehe, I'm afraid the power stops there... :P
 
 
5 hours later…
halirutan
halirutan
10:28 PM
Although the solution to this question seems easy, I find the description of the problem most disturbing:
> I am given a function say $f(x)$ on the real numbers. I would like to have the same function when $f(x)<\log(2)$ and if $x>\log(2)$ I want to have a zero function that is $f(x)=0$ for all $x>\log(2)$.
 
rm -rf
rm -rf
@halirutan Just a typo there... He means x < log(2)
 
halirutan
halirutan
@rm-rf Because the other way would be possible too: 
SetAttributes[f1, {HoldAllComplete}];
f1[(f_)[x_]] := If[f[x] < Log[2] && x > Log[2], f[x], 0];
and of course PiecewiseExpand[f1[f[x]]]
But this is not what is discussed in the comments.
@rm-rf I tried to find a canonical answer to Piecewise and its friends but haven't succeeded, so I thought about writing something up.
 

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