## How can I plot the function like this?...

I set a physical model for my reseach,

equ1 := x^4-5*x

equ2 := 1/x+x^2+3

x is a function of time t and it meets diff(x(t), t) = equi-equ2.

I want to plot the curve of x(t) varying with time

When I use the following command

DEplot({x(0) = 0, diff(x(t), t) = equi-equ2},x(t), t = 0 .. 20)   it shows: Error, (in DEtools/DEplot) called with too few arguments

Who can tell me what is wrong with my calculation? Thanks

Thanks

## clear one variable in maple...

hi

my code:

restart;

a := Matrix([1, 2, 3, 4, 5]); S := {}; ss := {};

for k to 5 do

S := `union`(S, {op(DirectSearch:-SolveEquations([a(1, k)*x+2+y = 0, x+y = 0])[3])});

ss := map(proc (c) options operator, arrow; rhs(c) end proc, S);

aaa := op(ss[[1]]); bbb := op(ss[[2]]);

"i want clear ss and then make ss as ss:={} in loop"

"for example if clear command clear ss variable"

"clear(ss)"

"ss:={}"

end do

## How do I use Maple to calculate the sample mean an...

If I have  the following..or different numbers, but 2 different arrays I need to calculate sample mean & variance

Array A:=([1,1,1,0,0,3,2,4])

and

Array B:=([2,1,0,1,3,3,4,1])

what formula do I use to force Maple 16 to calculate the sample mean and the sample variance?

## Using variables in a string...

I am trying to write a script that will read in vector files using ImportMatrix, perform a simple calculation then output a matrix file using ExportMatrix.

The difficulty I am having is that I would like to do this on a number of files,

eg.

for i from 1 to 600 do

Mi:=ImportMatrix(rowi):

do calc....

ExportMatrix(matrixi,Mi):

end do:

The variable i is in italics...

## How can I re-write this expression so it can be ev...

I have the following procedure that I am working with. I would like to store the result of the procedure in a variable called "result".

[code]
f := proc(result, x)
if x <= -7 then
result :=  1:
elif x > -7 and x <= 7 then
result := 2:
elif x > 7 then
...

## 3 variable function problem...

good say !

I want for my work to calculate the International Equation of State of Seawater

but when i enter my fonction in mapple: it is like mapple don't recognise the second variable s:

>t:= -> t;
s:= -> s;

> g :=(t, s)-> 999,842594+6,793952*10^(-2)*t-9, 95290*10^(-3)*t^2+1, 1685*10^(-4)*t^3-1, 120083*10^(-6...

## Minimize VaR with LP...

I want to minimze VaR (the 5th percentile for the return distribution) with LP.
However, the way I have specified the problem does not work for some reason, why?

restart:
with(Optimization):
with(LinearAlgebra):

nstock := 20:
n := 15:

R := RandomMatrix(n, nstock, generator = -15 .. 15, outputoptions = [datatype = float[8]]):
W := Matrix(nstock, 1, [seq(w[i], i = 1 .. nstock)]):
data1 := Array(Multiply(R, W));

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