@Christian Wolinski 

You got a thumbs up. Thank you very much. 

Is there a specific Maple programming book, you could surgest for future reading ? 

Truely great commands. Maybe you should consider doing a followup command which could show howto factor with steps. 

Meaning howto go from a^2+b^2+2*a*b to (a+b)^2. 

Cheers. 

@Carl Love 

I know the example doesn't hold up. I was just enquiry on howto overwrite variables. But many thanks for your answer, gave it thumbs up. Have a nice day.

And it was simply an attempt to make it draw the graph if you pass the extra parameter. 

Do you suggest locking it to a specific letter then? So It only responds, so that I type graph(x^2,g) only allows to plot x^2? 

Thank you, 

Its simply awsome.

@Rouben Rostamian  

Thank you for your answer. If you take here. How would find the inflexion points? 

x = [ 7.0, 7.2, 7.4 ,7.6, 8.4, 8.8, 9.2, 9.6, 10.0,10.4,10.8,11.2];

y = [ 0.692, 0.719, 0.723, 0.732, 0.719, 0.712, 1.407, 1.714, 1.99,2.118, 2.305, 2.711];

@acer 

Thank you for your answer, I discovered the solution myself. That if I inserted the functionchart command into a display. Then I was able to edit the y-axis. 

p.s. I am using Maple 2019.0 

@acer 

Sorry for that, English is not native language. So I sometimes overlook things. 

But thanks to the guide from Typos, I got it working :)

@acer 

There must be something wrong with my Maple installation :( Because the error, persists :  Error, invalid input: with expects its 1st argument, pname, to be of type {`module`, package}, but received MyLib

no matter if I use : 

LibLocation := "C:/temp/MyLib.mla";
LibraryTools:-Create(LibLocation);
LibraryTools:-Save(Mylib, LibLocation);
restart;
LibLocation := "C:/temp/MyLib.mla";
libname := LibLocation, libname;

or 

LibLocation:="C:/temp/MyLib.mla": # dir with write access
LibraryTools:-Create(LibLocation); # if the library is new
LibraryTools:-Save(MyMat, LibLocation);
restart;  # check
LibLocation:="C:/temp/MyLib.mla";
libname:=LibLocation, libname;
with(Mylib);

Its like Maple can't see the package ? :(

I am using Windows 10, 

I create the tempfolder as shown. But when I run the code, it creates the lib. However the error still persists. Any idea why?  

LibLocation := "C:/temp/MyLib.mla";
LibraryTools:-Create(LibLocation);
LibraryTools:-Save(Mylib, LibLocation);
restart;
LibLocation := "C:/temp/MyLib.mla";
libname := LibLocation, libname;
with(MyLib);
               LibLocation := "C:/temp/MyLib.mla"
libname := "C:/temp/MyLib.mla", "C:\Program Files\Maple 2019\lib"
Error, invalid input: with expects its 1st argument, pname, to be of type {`module`, package}, but received MyLib
 

@vv 

Thank you for your answer. It works, but when I try to call the package I sadly still get. 

Error, invalid input: with expects its 1st argument, pname, to be of type {`module`, package}, but received MyMat? 

I thank you all for your kind surgestions, 

What I am trying to achieve was an attepmt to build a test package, which can :

Do linear regression on two lists, and draw a plot or said regression formula. 

Using the argument LinModel(xliste,yliste). 

Where I do I put the plot argument? Inside of outside the procedure? 

thank you for your reply, 

How would I go about saving the model as a function? 

I have tried return f(x)=LeastSquares(xliste,yliste,x,curve=a*x+b), assign(f(x),LeastSquares(xliste,yliste,x,curve=a*x+b))

But get an about about left hand argument? 

@Kitonum 

Okay but if they weren't would that command return a result in degree? 

Note, I have tried with two planes who should have angle between them. But I still get a result in 

the form of arccos(...). 

Any thoughts? 

@Rouben Rostamian  

Hi I undstand what you mean, but thanks for your answer. 

The reason why I love to able to do the other thing in Maple is that couple of my students have had trouble understading what function-analysis is.  Thusly I would love to have to able to show it to them in Maple the way I surgest.