comp.soft-sys.math.mathematica Google Group

Re: Silly question on how to insert sections, subsections and etc. on a notebook

2013-05-24T09:23:59Z

Many many thanks

Re: Work on Basic Mathematica Stephen!

2013-05-24T09:26:01Z

Well it is frustrating but we can't just say that we could write great
documents using Mathematica but we have to actually do it and then try to
show them to a few individuals. Then maybe some of them will say: "That's
great, I want to do that also." Then maybe it will grow. I like to say: "The
great masterpieces have yet to be written."

Re: Work on Basic Mathematica Stephen!

2013-05-24T09:23:18Z

This is not an uncommon situation at colleges and universities.

Too many of the old fogies -- and, more dangerously, the "young fogies"
-- know about Ma. . t. .b and cannot imagine why anybody who needs to do
computing would use anything else. After all, it was good enough for
them. (Exception: Canadians who thing the same about M . . . e.)

Re: NURBS Package Available

2013-05-24T09:29:50Z

This package (IGES export of splines) is exactly what I need, but unfortunately the link is dead and a lengthy Google search did not reveal another source.

If anyone still has a copy of this package I'd be very grateful for a copy sent by email!!!

Many, many thanks in advance,
Robert.Herzog (at) freesurf.ch

Re: Silly question on how to insert sections, subsections and etc. on a notebook

2013-05-24T09:29:30Z

After change to Manual Grouping . . .

Select and cut the cell(s) to be "dangled" (at the end of the Section
but outside any Subsection), then paste them below the Section cell.

Next, close the Section group.

Now select the bracket of the closed Section cell along with the
now-separate cell(s) that you moved below the section.

How eigenvectors are normalized

2013-05-24T09:29:09Z

Dear Mathgroup,

When I use the function "Eigenvectors" how are the eigenvectors normalized?
Is it Euclidean norm equal to 1, with the largest component has imaginary
part equal to zero?

Thanks,
Ben

Re: Work on Basic Mathematica Stephen!

2013-05-24T09:28:47Z

I had to chuckle at your use of the word 'conceal'.....unfortunately, I
agree with your comment....mentioning Mathematica seems akin to
treason.....that was the reaction I felt...

-----Original Message-----
Sent: Thursday, May 23, 2013 10:00 AM
To: mathgroup

This is not an uncommon situation at colleges and universities.

Reduce an expression into a given form.

2013-05-24T09:28:27Z

Hello,

I have an expression of the form N[a,b,c]/D[a,b,c] with a, b and c some parameters on which N and D depend. I have to transform it into something like A[a,b]/c with A that does not depend on c. Is there any function in Mathematica that can do that?
Thanks a lot for any help.

Francesco

Re: Silly question on how to insert sections, subsections and etc. on a notebook

2013-05-24T09:28:07Z

Many thanks.

Suppose I want to modify the structure of an already-written notebook.
How to structure it as listed in my previous email? That is, part of it
goes to a section that it is divided in subsection 1, subsection 2 and
dangling cells. I want to select what set of cells go to subsection 1,

Re: Silly question on how to insert sections, subsections and etc. on a notebook

2013-05-24T09:27:46Z

It is not a silly question at all. The object is that you are writing a
notebook and discussing some topic in a section and then you want to include
a subsidiary discussion in a Subsection that would normally be closed and
then continue on with the main discussion. Another example is that you have

Re: Silly question on how to insert sections, subsections and etc.

2013-05-24T09:27:25Z

Hello

I wonder whether it would be possible to write a notebook with the following structure:

Section 1

Text and Mathematica commands

subsection 1.1

Text and Mathematica commands

subsection 1.2

Text and Mathematica commands

Text and Mathematica commands (note that part is not inside subsection 1.2 but it is inside Section 1)

Re: Work on Basic Mathematica Stephen!

2013-05-24T09:27:04Z

People are naturally interested in optimizing their jobs.
Teachers don't want to change their courses, learn new things, make hard
decisions like what to REMOVE from the course to make
space for Mathematica, or deal with Nuts.

If a teacher is shown a program that does the same thing as what he

Map

2013-05-24T09:26:43Z

I'm new to Mathematica and I've been given some code to help me analyse some data. I'm trying to understand what the Map function does, specifically what the {2,2} means?

qbarlist = Map[(# - bragg) &, hkllist,{2, 2}];

hklist is a 3 column list, bragg is a three element vector.

When I try the same line with {2} or {1} I seem to get the same answer. The online explanation of this term does not make that much sense to me. I'd be very grateful if someone could explain the purpose of the last term of the Map syntax.

Re: Work on Basic Mathematica Stephen!

2013-05-24T09:26:22Z

There are two subjects here, third party applications and collecting
useful routines that have appeared on the several groups.

It is difficult to collect and organize various routines that have
appeared on the groups. They may not be well enough developed and you
may not know where to put them so you can find them. Putting them in a

Re: ListPlot skips first point

2013-05-24T09:25:41Z

After updating to 9.0.1 the problem was resolved.

Thanks.

Re: How to use Mathematica find the solution of an

2013-05-24T09:25:21Z

The equation does not appear to have a solution except as a limit (from
below) but then the solution is either -1 or 1.

eqn = Arg[-(I/((1 + I w)^2 w))] == -Pi;

eqn // Simplify

False

eqn /. {{w -> -1}, {w -> 1}}

{False, False}

Limit[Arg[-(I/((1 + I w)^2 w))],
w -> -1, Direction -> 1] == -Pi

Re: How to stretch a image

2013-05-24T09:25:00Z

thank you for sharing on how to stretch an image. i have some c# image stretch codes i'd like to share with your guys. check the articles here. check here: [link]

Re: Average the same elements of the list

2013-05-24T09:24:40Z

data={{{a1,b1,c1},d1},{{a2,b2, c2},d2}};
{#[[1, 1]], #[[All, 2]] // Mean} & /@ SplitBy[data, First]

output:
{{{a1, b1, c1}, d1}, {{a2, b2, c2}, d2}}

data={{{a1,b1,c1},d1},{{a1,b1, c1},d2}};
{#[[1, 1]], #[[All, 2]] // Mean} & /@ SplitBy[data, First]

output:
{{{a1, b1, c1}, (d1 + d2)/2}}

Re: Comment about SetDirectory[]

2013-05-24T09:24:20Z

Yes, SetDirectory[NotebookDirectory []] works nice for me. After changing the
Export code (removing NotebookDiretory[]<>) and setting directory with
SetDirectory[NotebookDirectory []] I have no more problems with files placed
at wrong location.

Did you not try SetDirectory[NotebookDirectory []]

Re: expanding the use of symbolic computation in engineering .. was Re:

2013-05-24T09:23:39Z

I can only comment about my experience as well, but I beg to differ.

I believe my Mathematica-intensive sophomore course for materials
scientists has resulted in Mathematica as being the tool of choice for
the remainder of a student's undergraduate education---and know of many
cases where students continue to use Mathematica as a tool for graduate

Re: Silly question on how to insert sections, subsections and etc. on a notebook

2013-05-24T09:22:58Z

You could use the Cell menu item Grouping to change from the default
Automatic Grouping to Manual Grouping.

I often used to do that. My sad experience, though, is that sooner or
later this will get you into some sort of trouble, and you'd be much
better off structuring your notebook so as not to have any such

manipulate with user entered functions and variables

2013-05-23T07:56:40Z

I am trying to create a manipulate interface that would allow a user to enter a set of independent variables and a function of these variables. The program would then return calculations based on partial derivatives of the function with respect to the given variables. Eventually this would lead to an error propagation program for undergraduate physics labs.

Re: Work on Basic Mathematica Stephen!

2013-05-23T07:56:19Z

David...

But that was exactly my point...I tried so hard with our Community College
and University to get Mathematica into the curriculum....or, as I said, to
give some lectures and examples on the use of Mathematica....and ALL of
them, Engineering, Math and Physics Depts said 'Thanks but No Thanks', as

Re: Average the same elements of the list

2013-05-23T07:55:59Z

data = {{{a1, b1, c1}, d1}, {{a2, b2, c2}, d2},
{{a1, b1, c1}, d3}, {{a2, b2, c2}, d4},
{{a1, b1, c1}, d5}, {{a3, b3, c3}, d7}};

For v7 and later

sol = Plus @@ #/Length[#] & /@
GatherBy[data, First]

{{{a1, b1, c1}, (1/3)*(d1 + d3 + d5)},
{{a2, b2, c2}, (d2 + d4)/2}, {{a3, b3, c3}, d7}}

Silly question on how to insert sections, subsections and etc. on a notebook

2013-05-23T07:55:38Z

Hello

I wonder whether it would be possible to write a notebook with the following structure:

Section 1

Text and Mathematica commands

subsection 1.1

Text and Mathematica commands

subsection 1.2

Text and Mathematica commands

Text and Mathematica commands (note that part is not inside subsection 1.2 but it is inside Section 1)

Re: ListPlot skips first point

2013-05-23T07:55:18Z

Reverse your data1 and data2 variables.

Show[ListLogPlot[data2, PlotStyle -> Red, Joined -> True,
PlotRange -> {{0, 20}, {0.001, 100}}],
ListLogPlot[data1, PlotStyle -> Blue, Joined -> True]]

I don't know why that works, but it does. :o

Re: Average the same elements of the list

2013-05-23T07:54:58Z

Something like

{#[[1,1]],Mean[#[[All,-1]]]}/@ GatherBy[data/.{a__,d_}->{{a}, d}]

should work

Re: Work on Basic Mathematica Stephen!

2013-05-23T07:54:37Z

It will be done by example. Several people will work together,
exchanging Mathematica notebooks or working on a common notebook. The
notebooks will be what I call "literate"; they will look something like
a technical paper or report, but they will take advantage of all the
active and dynamic features of Mathematica, and contain generated

Re: Comment about SetDirectory[]

2013-05-23T07:54:17Z

Did you not try SetDirectory[NotebookDirectory []]
to set it once and be done with it?

Re: ListPlot skips first point

2013-05-23T07:53:57Z

Interesting. When I copy and paste from your post it appears to
me the first point is plotted whether or not the last point in
data2 is deleted. This with

In[12]:= $Version

Out[12]= 9.0 for Mac OS X x86 (64-bit) (January 24, 2013)

Re: Average the same elements of the list

2013-05-23T07:53:37Z

You didn't specify what to return in case the first elements of the
sublists are NOT all the same; let's return the entire original list in
this case. Then perhaps something like the following will do.

op[lis_] :=
If[And @@ MapThread[Equal, First /@ lis],
{First@First@lis, Mean[Last /@ lis]},

Re: ListPlot skips first point

2013-05-23T07:52:56Z

When I evaluate your statements (using Show) in M 9.0.1 on Windows the first
point of data2 is plotted.

The following is a more detailed plot using Presentations with the points
shown and Tooltips on the data2 points, clearly showing that the first point
is used.

<< Presentations`

yticks = CustomTicks[Log, {-4, 3, {1.}, {2, 5}}];

Re: Average the same elements of the list

2013-05-23T07:49:53Z

datanew = {data[[1,1]], Mean@Pick[data[[All,2]],data[[ All,1]],data[[1,1]]]}

Re: ListPlot skips first point

2013-05-23T07:53:16Z

I see this problem with v 9.0.0.0, but this does not occur with v 9.0.1.0
under Mac OS X 10.8.3

Bob Hanlon

Re: Comment about SetDirectory[]

2013-05-23T07:52:35Z

I've seen one other case.
It was when the directory containing NotebookDirectory[] was deleted (by someone else on a shared disk).

For example,
temp.nb is written to ~/tmp/foo.
~/temp/foo is deleted with the notebook still open (a warning is dialog comes up.)
But:
NotebookDirectory[]
yields:

Re: ListPlot skips first point

2013-05-23T07:52:15Z

It plots fine for me. Windows 7, V9.0.1.

Kevin

expanding the use of symbolic computation in engineering .. was Re:

2013-05-23T07:51:55Z

...

I think your experience is typical, and that the "sweet spot" for
engineering computation is not in symbolic computation nor Mathematica
in particular. Certainly educators don't view symbolic computation
as key to any particular course that is in the core curriculum. See
for example...

Re: Work on Basic Mathematica Stephen!

2013-05-23T07:51:35Z

There have been discussions about this among the users of
[link]

I agree that Mathematica does have a need for more communication
between users, and especially sharing code. As Ingolf mentioned,
there's library.wolfram.com, but I don't think most people will go

Re: Average the same elements of the list

2013-05-23T07:51:14Z

Elegance is often a matter of individual taste (it lies in the eyes of the
beholder?), but a possible way is
datanew:=If[data[[1,1]]==data[ [2,1]],{data[[1,1]],Mean[{data [[1,2]],data[[2,2]]}]},data]
data={{{1,2,3},4},{{1,2,3},5}} {{{1,2,3},4},{{1,2,3},5}}
datanew{{1,2,3},9/2}
data={{{1,1,3},4},{{1,2,3},5}} {{{1,1,3},4},{{1,2,3},5}}

Using manipulate with user entered variables and functions

2013-05-23T07:50:54Z

I am trying to create a program through which a user can enter a number of
variable names and a function of those variables. The program then performs calculations based on derivatives of the function with respect to the entered variables. Eventually this will become a tool for error propagation in an undergraduate physics lab.

Re: Overriding the single quote (')

2013-05-23T07:50:34Z

Of course, I expect to design a package that can avoid the gotcha's which will also mean plenty of testing and MUnits.

How to use Mathematica find the solution of an equation when Arg is part of it?

2013-05-23T07:50:13Z

Hello

I need to solve the following equation:

Arg[-(I/((1+I \[Omega])^2 \[Omega]))]==-\[Pi]

I have tried Solve (empty output), Reduce (it gives some results but not
the answer Omega=1) and FindRoot (it gives Omega=1 but it is a
numerical search). Is there a way to get the solution not using a

Average the same elements of the list

2013-05-23T07:16:14Z

Hello,
I have list which is something like
data={
{{a1,b1,c1},d1},{{a2,b2,c2},d2 }}
I would like to get new list which gets average of the second elements if the first elements in the sublists are all the same.
Namely if a1=a2,b1=b2,c1=c2
new list would look like
datanew={{a1,b1,c1},Mean[{d1,d 2}]

Average the same elements of the list

2013-05-23T07:19:59Z

Re: NSolve Question

2013-05-23T07:16:19Z

Hard to know exactly what you did because there is some traditional form, I guess, in what you show. My guess is the issue is in the definition of v[t_], wherein the pattern underbar was omitted. That would mess up the definition in a way that would make g3[t] give a bad result.

Here is code that seems to work.

Unable to generate any initial points with NMaximize (or NMinimize)

2013-05-23T07:16:08Z

I often get the error:

NMaximize::incst: NMaximize was unable to generate any initial points satisfying the inequality constraints

while there are clearly points satisfying the inequality constraints. For example:

NMaximize[{1/(0.` + (0.012710615354858255` (0.07879657698200958` +
a) (0.000046296899009293725` +

Re: setting highlight color and font size

2013-05-22T06:18:43Z

Yes, this would work for me, but I'll be converting the whole thing to
CDF for my wife's use (it's a cash-flow projection pgm) so that method
isn't going to be very effective. I'd like to make it user-proof.

Thanks for all these examples, they illustrate your point effectively.

- Dushan

ListPlot skips first point

2013-05-22T06:18:38Z

In the particular example below, the first point of data2 is *not* plotted. If I drop the last point of data2, then the first point comes into view. Not sure why.

data1 = {{1, 11.07}, {120, 11.07}};
data2 = {{1, 11.07}, {2, 2.15}, {3, 0.83}, {4, 0.43}, {5, 0.26}, {6,
0.17}, {7, 0.12}, {8, 0.09}, {9, 0.07}, {10, 0.06}, {11,

Re: Comment about SetDirectory[]

2013-05-22T06:18:32Z

John,

The case I had mentioned is related to creating an animation based on
Dynamic interface. I know that it is not straightforward way but it was
simplest since I originally made a Dynamic presentation and the easier way
was just Export a Table of frames each has different value of a time-related

Re: Comment about SetDirectory[]

2013-05-22T06:18:27Z

I've never heard of or seen Alexey's issue before. However, it is the
case that NotebookDirectory[] will return $Failed if you execute
NotebookDirectory[]:

* in a notebook which hasn't been saved to disk, and therefore doesn't
have a notebook.
* in an evaluation which wasn't directly triggered by a specific