@Kitonum Thanks,  i thought that i can use  labels = ["x values", "y values"] if axis[2] = [color = white]

It's really not good thing with Maple not to have labels and axis indépendant in options. Hope some change for next upgrading.

@Markiyan Hirnyk Oh sorry!

@acer Thanks for your response, convert do what i want.

@acer Thanks for your example, i'm a beginer with maple. Your example showed me how can i overload an operator as '*'.

First i thought that my question was really simple. I want just to get always the exact decimal result without any rounding and without changing the Digits value.

@Axel Vogt 

what about if a := 0.1111111111121213123131? so i have to change the values of Digits to greater value than 10.

@Christian Wolinski 

i get this:

0.01524157872 .. 0.01524157877

but i did't understand what are trying to do with this boundaries.

@Christian Wolinski 

Error, (in minimize) unexpected options: {k, k}, {k = 0 .. 1, k = 0 .. 1}

@Majmaj 

well if i have 2 numbers with number of décimals number "d1" for the first and "d2" for the second then i want the result to be with d1*d2 decimals.

well i have a proc roundNumber(number, decimalsNumber):

roundNumber( .123456789 * .123456789, 15) return 0.01524157875

to fix the problem i have to do this, and i don't like the idea:

that returns what i need 0.015241578750191.

@Markiyan Hirnyk I think that if you do .123456789*.123456789 by hand you will get the sense of 0190521. 

Thank you so much @epostma

i will use zip a $ operator next time ;)

@Markiyan Hirnyk 

Thank you ... i undestand now how Maple evaluate the standard deviation.

So i have to this

L := [3, 2, 2];

W := [7, 5, 8];

weightsSum := PartialSums(W)[nops(W)];

weightsSquaredSum := PartialSums( [seq( W[i]^2, i = 1 .. nops(W) ) ] )[nops(W)];

adjustmentFactor := sqrt( (weightsSum^2 - weightsSquaredSum) / (weightsSum * (weightsSum-1)) );

StandardDeviation(L, weights = W) * evalf(adjustmentFactor);

0.4893604850006769

My question now is why Maple do the calculation with a formula that most of my my books  didn't talk about?

@Preben Alsholm Thanks its really clear now.

@Carl Love Thanks a lot. The examples were usefull to understand. The philosophy of Maple is unique ;) Now i can find the equivalence between C programming and Maple for passing variables by references.

Thank you again you are so kind.

@Carl Love thanks it works but i don't understand really why ... even if i have read the eval help.

@Preben Alsholm The print statement produce an ouput : that is "y" without its evaluation. If i add eval as suggested by Carl, i got an ouput with the evaluation of y.