## Multiplying Vectors and Matrices (more than 2 in t...

with(LinearAlgebra):
a:=Vector([1,2]);
b:=Matrix([[1,2],[1,2]]);

Say if I need a^T * b * a, I will do this:

VectorMatrixMultiply(Transpose(a), b);
VectorMatrixMultiply(%, a);

But this seems too long for such a simple matrix （and vector) computation. I am sure there must be an short way.

What if I need more computation, like

a^T * b * c*d*f*g* a, where c,d,f,g are other 2x2 matrices.
If I were to use the above command, that'll take a long time to input.

Thanks,

## differentiate a function with respect to a vector ...

f:=x+y+y;

diff(f,x);
diff(f,y);
diff(f,z);

What I hope to get is a vector with i-th entry being the dervative of f, differentiated w.r.s.t the i-th parameter, like this

Vector([1,1,1]);

Is there a more efficient (built-in) command to do this?

VectorCalculus[diff] does not do what I want.

Thanks,

casper

## how to delete a plot from the worksheet?...

Hi Maple friends.

I have a plot. I click on the plot, and the blue border appears the around the plot. I press the delete key on my keyboard, and the plot is not deleted. Not deleted when I press the backspace key either. I can right-click on the plot and choose 'cut', but that just copies the plot to the clipboard.

So how can I delete a plot from the worksheet, without deleting anything else?

## differentiating cosec and cot...

Hi Maple friends.

I am trying to differentiate these:

1. csc(x)/x

2. 3*x^2*cot(x)

From doing it by hand, I am getting:

1. -cosec(x)*(xcot(x) + 1)

2. 6x*cot(x) - 3x^2*cosec^2(x)

But Maple is giving the answer:

1. diff(csc(x)/x, x);

-csc(x)*cot(x)/x-csc(x)/x^2

2. diff(3*x^2*cot(x), x);

6*x*cot(x)+3*x^2*(-1-cot(x)^2)

My answers don't look like Maple's answers. Are they actually the same?

## Symbols are missing in Maple 18...

Whenever i open Maple 18, some symbols are missing including the arrows. I use Maple 18 to do math assingments, and the arrows are useful. It seems like a lot of other content is missing in Maple 18 as well. Below is a picture of the missing symbols, or there should be one. Any help on how i get the arrows back, would be amazing.

## Why do I get this error message with Nonlinearfit?...

Here is my code & the error mesage.  What's wrong?

with(Statistics);
X := Vector*([0, 5, 10, 15, 20, 25, 30], datatype = float);
Y := Vector*([38.8, 53.8, 82.4, 107.6, 130.7, 152.4, 173.2], datatype = float);
NonlinearFit(av^2+bv+c, X, Y, v);
Error, (in Statistics:-NonlinearFit) invalid input: PostProcessData expects its 1st argument, x, to be of type {array, list, rtable}, but received w

## Saving a graphic as VRML...

Hello,

It seems that the command vrml is long gone (I have a lot of worksheets using this "command") and

has been replaced by saving  a graphic in x3d format.

That's ok I have a x3d renderer but the quality of Maple for the x3d format in not very good (for the moment).

Jean-Michel Collard

## how to export numerical evaluations immediately to...

for example i want to save the Square root of 2 to 1000000 decimal place to an ascii text file ...

i used the writeto command after evalf[100](sqrt(2)) for but it contains line breaks and \ character in output !

but i only need the pure continues 1000000 digits !

please guide me on this simple request ?

## get the function, from a table of values...

Hi Maple friends.

If I have a table of values, how can Maple provide the function?

For example:

x=10,15,20,25,30,35,40

y=2.01,4.87,6.50,9.875,14.00,18.90,24.40

How can Maple find out the y function with respect to x?

## Identify arguments passed to cmaple (windows)...

Hi all,

Sorry if the question of the title wasn't very clear. I am not sure how to express it correctly.

But here is what I do for linux,

and I get

So when I submitted a lot of jobs, I can see the arguments that was passed to it. I can easily kill a process.

How do I do that in windows if anyone knows?

Here is a screenshot from windows task manager:

That does not give informative details, just like the 'top' command in linux.

Thanks,

How to make Decimal number in maple by default?

How to make radian to degrees? Think It is like this "degcos" but I cant see the correct result, because it is not showed in decimals

Why do I have to active all my varibles when I open the document after I have saved it?

Regards

Østerbro

## JavaViewLib with Maple 18...

Does anyone have JavaViewLib running on Maple 18?  Could you help me out?  I can't get it running and I really need a way to export some 3d plots to a web page where a colleague can view them (rotate and such).

## Conditions in NonlinearFit?...

Hello everyone,

I'm trying to do some fitting using NonlinearFit, for the coefficients I know in advance, that they have to fulfill a condition (a+b>c+1). I couldn't find a way to make Maple take this condition into consideration while fitting my data. I tried to use Parameterrange to make the difference a+b-c+1 positive, this works for linear conditions like mine but leads to computational difficulties and errors like "no improved point could be found".

Sören

## Pixel Conversion

by: Maple 18

Here is an example of manipulating an Array of pixels. I chose the x-rite ColorChecker as a model so there would be published results to check my work. A number of details about color spaces have become clear through this exercise. The color adaptation process was modeled by converting betweenXYZ and LMS. Different black points may be selected depending on how close to zero illuminance one would accept as a good model.

I look forward to extending this work to verify and improve the color calibration of my photography. Also some experimentation with demosaicing should be possible.

 Initialization

x-rite Colorchecker xyY Matrix

=

=

 Convert xyY to XYZ

=

 XYZ D50 to XYZ D65

=

Convert XYZ to Lab (D50 or D65 White Point)

 Reference White Point for D50  =  =  = Lab Conversion Constants; Reference White Point for D65  =  =  =

=

Convert XYZ to aRGB (XYZ D50 or D65 to aRGB D65)

XYZ Scaling for aRGB Ymax,Ymin (Ref. Adobe RGB (1998) Color Image Encoding Section 4.3.2.2 and 4.3.8)

 White Point (Luminance=160Cd/m^2) D65 Black Point (Luminance=0.5557Cd/m^2) D65 White Point (Luminance=160Cd/m^2) D50 Black Point (Luminance=0.5557Cd/m^2) D50 =  =  = =  =  =

aRGB Expansion for 8bits

Combine Steps

Note: The aRGB values published for ColorChecker assume a black point of 0cd/m^2.

=

=

 Convert XYZ to ProPhoto RGB (D50)

=

 Convert XYZ to sRGB (XYZ D50 or D65 to sRGB D65)

Note: The sRGB values published for ColorChecker assume a black point of 0cd/m^2.

=

=

Corrections to the original version of theis document;
 Make the scaling for a nonzero black point the same for all RGB color spaces.
 Clip negative RGB values to zero.
 Remove the redundant Array container from matrix multiplications.
Use map in place of the \$ to apply a function to each element of an Array.

## Write string to file...

Hi,

I would like to a string of characters to a file. For example,

***

str:="hello world";
WriteFile[APPEND]("D:\\output3.txt", str);

***

It doesn't work. I did not get output3.txt :(  How should I do, to write a string of characters, such as "hello world" to a file?

Thank you

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