## Sort contents of Record...

Asked by:

Hi

I have a long column vector containing data in Records.

A:=Vector[column](4, [J_K = `Record(mu = 724.901557888305, sigma = 96.7437910529146)`, I_W = `Record(mu = 775.098442111694, sigma = 96.7437910529198)`, K_J = `Record(mu = 785.098442111694, sigma = 96.7437910529198)`, D_B = `Record(mu = 764.901557888305, sigma = 96.7437910529146)`])

How to I sort this in descending values of mu so I get:

Vector[column](4, [K_J = `Record(mu = 785.098442111694, sigma = 96.7437910529198)`,I_W = `Record(mu = 775.098442111694, sigma = 96.7437910529198)`,D_B = `Record(mu = 764.901557888305, sigma = 96.7437910529146)`,J_K = `Record(mu = 724.901557888305, sigma = 96.7437910529146)`])

Im aware you can extract mu from Records by the rhs(A[1]):-mu

## Multiple plot in one figure...

Asked by:

Hello every body

I have three vectors `X`, `Y` and `Z`. I need to plot `X` vs `Z` and `Y` vs `Z` in one plot. How can I do this?

Thanks in advance

## How to extract only positive elements of a big vec...

Asked by:

I have a big vector (1*10000) composed of negative, positive and HFloat(infinity) elements. How to extract only positive elements of this messy big vector with corresponding number of element,except positive infinities?

For example, suppose only the 111,181, 206th elemenst of this vector are positive values as: 101.2109e11,19211.129,87211.

How to get both 111,181, 206 and their corresponding values, 101.2109e11,19211.129,87211?

## define a vector from 2 points...

Asked by:

Something simple.

Two points and there doesn't seem to be an internal command to define a vector from it.

say for example we have p=(3,6,-1) and q=(4,-2,2)

How to write pq and have the answer of q-p as a vector returned?

## Displacement and distance traveled with vectors

Maple 18

In this app you can use from the creation of curve, birth of the position vector and finally applied to the displacement and the distance traveled. All this application revolves around the creation of a path and the path of a particle over this generated by vectors. You will only have to insert the vector components and the times to evaluate. Designed for engineering students guided through Maple. In Spanish.

Video

https://www.youtube.com/watch?v=jOcKYZ5EEM0

Lenin Araujo C

Ambassador of Maple

## Shortcut in Vectors for Engineering

Maple 18

Here in this video you can observe the correct insertion of vectors; Making use of the keyboard, ascii code and tool palette of our Maple program. As our worksheet is very large, I made the explanation in two parts; I recommend that you observe this first part of performing any execution on your Maple worksheet. You can contrast your results with the apps also made in this software. In Spanish.

Shortcut_in_Vectors_for_Engineering.mw

Movie # 01

https://www.youtube.com/watch?v=EJtAli54q_A

Movie # 02

https://www.youtube.com/watch?v=m-JUmhkbWI8

Lenin Araujo Castillo

Ambassador of Maple

## weighted norm of an expression...

Asked by:

how can we compute wighted norm of a matrix or a vector in maple?

## Plot of Position Vector in Maple

Maple 18

As you can see this app performs the trace of a given path r (t), then locate the position vector in a specific time. It also graphs the velocity vector, acceleration, Tangential and Normal unit vectors, along with the Binormal. Very good app developed entirely in Maple for our engineering students.

Plot_of_Position_Vector_UPDATED.mw

https://youtu.be/OzAwShHHXq8

Lenin Araujo Castillo

Ambassador of Maple

## Error for the Vector constructor...

Asked by:

The following construction of a simple vector of matrices (just a test example)

`Vector(2,(a) -> Matrix(2,2,(b,c) -> m||a||b||c));`

works in Maple 17, but not in Maple 2017 where the error message "Error, (in Vector[column]) number of elements on right side must match subselection on left side" is produced. Why that?

Update: If no output is prompted, i.e., if the above line is terminated with colon instead of semicolon, then no error is raised. What?!

## Kinematics Curvilinear

Maple 18

With this application the components of the acceleration can be calculated. The components of the acceleration in scalar and vector of the tangent and the normal. In addition to the curvilinear kinetics in polar coordinates. It can be used in different engineers, especially mechanics, civilians and more.

In Spanish.

Kinematics_Curvilinear.mw

Lenin Araujo Castillo

Ambassador of Maple

## How to convert an imported data to Vector?...

Asked by:

A very big data was imported by me through

```data := Import("http://fs3.fex.net/get/245716150875/11071260/data.txt");
"3.0994584798345
22.889020258043
....

26.082759642081
42.911810680717
6.4578968130322"

```

I need to convert it to Vector/Array. Now its type is "string":

```whattype(data);
string
```

Here is my unsuccessful attempt:

```convert(data,Vector);
Error, invalid input: `convert/Vector` expects its 1st argument, V, to be of type {Array, Matrix, Vector, array, sequential}, but received 3.0994584798345
22.889020258043
....```

data.mw

## How do I solve a system in two unknown vectors?...

Asked by:

I'm trying to solve the really simple system u+v = <-2,4> and u-v = <-3,6> for u and v using Maple. My attempt attached.

Download solve_error.mw

Why do I get this error? How might I get the solution?

## Display a list of equations in column...

Asked by:

Hello,

I have a list of equations. I would like to display this list in column.
Problem : as each term of my list is an equation, i can not transform my list in a vector.
How can I do to display a list of equations in column ?

Thank you for your help.

## Vectorization of Symbolic Functions...

Asked by:

Maple provides efficient vectorization and automatic parallelization for many common operators. For example

`x -> 2*~x*~cos~(x*~x)`

But in my application it is common to want to create rather long vectorized operators starting from some complicated symbolic computations. Doing conversions by hand from symbolic expressions to element-wise operations is laborious and error prone.

As a very simple example consider that it is possible to obtain (almost) the same result as above by writing the following as a vectorized operation

`D(x->sin(x^2))~`

But there are at least two problems with this. First of all it is not nearly as efficient as the first operator and second, perhaps not unrelated, is that the datatype returned when applying this operator to a Vector/rtable of hardware floats (e.g. datatype=float[8]) becomes something  more general.

My question is how can I convert a complicated symbolic expression into an efficient numeric element-wise vector operation?

I have tried several different approaches but so far without success. In the case above for example it seemed natural to expect that the following derivative

`D(x->sin~(x^~2))`

would produce a vectorized result, but this is not the case. In another attempt I was unable to see how to perform substitions into an expression, e.g. like this

`unapply(subs(`*`=`*`~, cos=cos~, diff(sin(x),x)), x)`

I would be glad to receive suggestions and/or references to relevant documentation.

## element by element vector multiplication...

Asked by:

I found the following:

Does this not apply to vectors?  If not what syntax is required?  I cannot seem to execute this simple operation which I can easily do in MATLAB.  If you have such a capability why is it not clearly documented in the HELP pages?

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