I want to split a arbirtray list of elements by position into two new lists containing all the even and odd elements.

Example: With a list like this:

ls:=["a", "b", "c", "d", "e"]

how can I get two lists like this:

["a", "c", "e"], ["b", "d"]

How to do it in Maple ? Thanks！ 

Maybe selectremove is useful?

colect(expr,y)  and collect(expr,y,factor) do not work on these.  The expression can be anything. No necessarily a polynomial in y.

I have as input an expression, which has y  in it, and I want to find if I can write it  as   y*(....)  of y^2*(...) or y^3*(...), etc...

Basically, I want to see if y can be taken out as common term. Just like we do by hand. 

So, given expression as  y^2+y^3*sin(x)+3*x*y^5 then I want to see if it can be written as y^2*(1+y*sin(x)+3*x*y^3)

In the above y^2 was extracted as common term. I found that simplify sometimes work, but I can't depend on simplify, since it is not guranteed to work all the time. Here is an example where it worked

expr:=y^2+y^3*sin(x);
simplify(expr)

but if expression is this, then it did not extract out y^2

expr:=y^2+y^3*sin(x)+3*x*y^5;
simplify(expr)

I am doing this  all in code, without looking at the expression and decide what to do. 

I just know  y is the name of the variable, and the expression will be a function of y  and I just want to know if I can extract a common y^n  term out, so the result is y^n*g(y)

For example, for expr:=y^2+y^3*sin(x)+3*x; it will fail, since  I can't extract y from all terms. In this case the result will be  y^2*(1+y*sin(x))+3*x  and this is not type(`*`). So it is ok for the method to fail, if it can not do it. I can always check the result to see if it failed or not.

Does Maple have build in method to do this? Or one has to program this? I wanted to ask first before if there is some hidden Maple function that can do this I did not see.

Sometimes math is easier to do by hand than using the computer :)

Maple 2020.2

Thanks.

edit: I also tried factor, but it does not work on everything. An example where it did not work

expr:=y^2+y^3*sin(x)+3*x*y^(7/2);
factor(expr);

It did not factor out y^2 because of y^(7/2) is not "integer, rational. numeric, or algebraic coefficients"? according to help.

Edit:

Thanks to all the answers. I used a combination of all of them to check if it can be factored or not, and now it is working for every example I tried it on. So if one method failed, I try the next method shown in the answers. 

Dear maple users.

Greetings for the day.

I hope you are all fine and safe.

In the below mention code, I need to plot "ax" at 0..1 when N=1 and N=2.

But the code only working for the N=0 case.

How to tackle this situation and plot the function for various values of "ax" at ax=0..1.

waiting for your reply.

JBV.mw

Code:

restart;
PDEtools[declare](f(x), t(x), g(x), prime = (x));

N := 2; m := .2; pa := 3.14*(1/3); ax := ax; h2 := 1+.2*ax+.3*sin((2*3.14)*(ax-.2)); h1 := -1-.2*ax-.1*sin((2*3.14)*(ax-.2)+pa); a2 := 1.4+.1*sin((2*3.14)*(ax-.2))+.3*sin((2*3.14)*(ax-.2)+pa);

f(x):=sum(p^j*f[j](x),j=0..N);  t(x):=sum(p^j*t[j](x),j=0..N);

g(x):=sum(p^j*g[j](x),j=0..N);

Eq1 := (1-p)*(diff(f(x), `$`(x, 4)))+p*((1+.2)*(diff(f(x), `$`(x, 4)))-(.2*(1/3))*(diff((diff(f(x), `$`(x, 2)))^3, `$`(x, 2)))-2*(diff(f(x), `$`(x, 2)))+diff(t(x), `$`(x, 1))+diff(g(x), `$`(x, 1)));

Eq2 := (1-p)*(1+1.2)*(diff(t(x), `$`(x, 2)))+p*((1+1.2)*(diff(t(x), `$`(x, 2)))+.1*(diff(t(x), `$`(x, 1)))*(diff(g(x), `$`(x, 1)))+.2*(diff(t(x), `$`(x, 1)))^2+.5*(diff(f(x), `$`(x, 1)))^2);

Eq3 := (1-p)*(diff(g(x), `$`(x, 2)))+p*(diff(g(x), `$`(x, 2))+diff(t(x), `$`(x, 2)));

for j from 0 to N do
equ1[j] := coeff(Eq1, p, j) = 0; 
equ2[j] := coeff(Eq2, p, j) = 0;
equ3[j] := coeff(Eq3, p, j) = 0;
end do;

con[1][0] := f[0](h2) = (1/2)*a2, (D(f[0]))(h2) = 0, f[0](h1) = -(1/2)*a2, (D(f[0]))(h1) = 0; con[2][0] := t[0](h2) = 1, t[0](h1) = 0; con[3][0] := g[0](h2) = 1, g[0](h1) = 0;

for i to N do

con[1][i] := f[i](h2) = 0, (D(f[i]))(h2) = 0, f[i](h1) = 0, (D(f[i]))(h1) = 0; con[2][i] := t[i](h2) = 0, t[i](h1) = 0; con[3][i] := g[i](h2) = 0, g[i](h1) = 0 end do;

for i from 0 to N do
P:=dsolve({equ1[i],equ2[i],equ3[i],con[1][i],con[2][i],con[3][i]},{f[i](x),t[i](x),g[i](x)}):
f[i](x):=rhs(P[1]);
t[i](x):=rhs(P[2]);
g[i](x):=rhs(P[3]);
end do:

f(x):=evalf(simplify(sum(f[n](x),n=0..N)));
Am := (1+.2)*(diff(f(x), `$`(x, 3)));
with(plots);

display(plot(eval(Am, x = .6), ax = 0 .. 1, numpoints = 200, color = blue));
 

Digits := 6:
f := (t,x,y) -> diff(x(t),t$2) = -x(t)/(x(t)^2+y(t)^2)^(3/2):
g := (t,x,y) -> diff(y(t),t$2) = -y(t)/(x(t)^2+y(t)^2)^(3/2):

t0 := 0:
x0:=1: y0:=0: tf := 3: n := 12:                 # number of subintervals
m := 2:                  # to print every mth step
h := evalf((tf - t0)/n): # step size

t:=t0: x:=x0: y:=y0:

fmt := `%10.0f %10.4f %10.4f \n`:

for i from 1 to n do
   k1 := f(t,x,y):
   l1 := g(t,x,y):                    # left-hand slopes
   k2 := f(t+h/2,x+h*k1/2,y+h*l1/2):
   l2 := g(t+h/2,x+h*k1/2,y+h*l1/2):  # 1st midpt slopes
   k3 := f(t+h/2,x+h*k2/2,y+h*l2/2):
   l3 := g(t+h/2,x+h*k2/2,y+h*l2/2):  # 2nd midpt slopes
   k4 := f(t+h,x+h*k3,y+h*l3):
   l4 := g(t+h,x+h*k3,y+h*l3):
   k := (k1+2*k2+2*k3+k4)/6:
   l := (l1+2*l2+2*l3+l4)/6:
   x := x + h*k:
   y := y + h*l:
   t := t + h:
   if trunc(i/m) =i/m then  printf(fmt,180*t,x,y) fi; od:
Error, (in f) invalid input: diff received 0, which is not valid for its 2nd argument
 

What do you suggest for graphics that are very close to each other in one figure? 

I am asking for graphics in articles to be sent to a scientific journal.

a simple example

restart:
with(plots):
f1:=x->0.95*x;
f2:=x->0.99*x;
f3:=x->0.991*x;
p1:=plot(f1(x),x=0..2,color=red);
p2:=plot(f2(x),x=0..2,color=blue);
p3:=plot(f3(x),x=0..2,color=green);
display(p1,p2,p3);

Is there anyone able to solve this integral for me?

Hi, 
I wonder what is I in MAPLE?
Obviously I is not an indeterminate

z := a+I*b:
indets(z);

# but

has(z, I)
                             {a, b}
                              true

What does this answer mean:

whattype(I);
                   complex(extended_numeric)

I would have thought that  I was some kind of protected symbol such as Pi, but it's not

attributes(Pi);
attributes(I);
                           protected

In fact, trying to assign 1 to I just returns an error saying this is not legal assignment

I:=1
Error, illegal use of an object as a name

So, what is I in Maple?

Thanks in advance

Dear all,

I have a long Maple code.

After running the code, suppose that we get an error in one of the lines.  I can't simply find the mouse cursor in the line which includes the error.

Question 1: How to find quickly which line has the error? What are your solution methods?

Question 2: Enlarging more or highlighting the cursor mark maybe works. Is it possible?

When i trying to solve the BVP the following error will found 

Error, (in fproc) unable to store 'HFloat(1.0141653815612295)+HFloat(0.0020355870386861838)*I' when datatype=float[8]
 

I have attached my worksheet.

Please anyone help me to get solution to this problem.

Thank you so much

Download Main.mw

Hello Maple friends,

I use Explore() often and noticed something today which seems like either a bug or an error on my usage.

I have a long worksheet where I use Explore at one point to show the behavior of an expression relative to one parameter assigned to a slider. Later in the sheet however, I re-assign some of the variables used in that expression and I call Explore again to see how the expression behaves with the different parameters.

The issue is that when I move the slider on the first explore, the result is incorrect because it seems to be using the values of the variables at the end of the worksheet, not the variables at the point the Explore statement exists.

I would expect Explore to make a copy of the stack at the point it gets called such that the result is correct in the context of its location in the worksheet.

Is this the correct behavior and is there a way to make this work as expected? The only workaround I have in mind is to rename the variable names just to make Explore work, which doesn't seem like a great solution.

Thanks.

blessing.mw please i really need your help on this, i have been trying to fix this error for a while now. 

I have function that accept keyword argument. From this function, I need to pass this argument to another function using the same signature and using same name for the keyword. But it is not possible to do. 

Easier to explain with an example.   This is what I want to do

restart;
foo:=proc(n::integer,{ic::`=`:=[]})   
   post_process(n+1,'ic'=ic);
end proc;

post_process:=proc(n::integer,{ic::`=`:= []})
    print("in postprocess, n=",n, "ic=",ic);
end proc;

foo(3,'ic'=(y(0)=5))

Gives 

The problem is that when calling post_process(), using 'ic'=ic it does not work. Currently I have to change the keyword name as workaround, like this

restart;
foo:=proc(A::integer,{ic::`=`:=[]})
   print("in foo, A=",A, "ic=",ic);
   post_process(A,'new_ic'=ic);
end proc;

post_process:=proc(A::integer,{new_ic::`=`:= []})
    print("in postprocess, A=",A, "ic=",new_ic);
end proc;

foo(3,'ic'=(y(0)=5))

Which gives

Now it passed it. I would have liked to keep same keyword name ic in both function signatures instead of coming up with new name.

Is there a way to do that? 

This is not the only problem. The problem with this workaround, is that it does not work when the keyword argument is not passed to the first function. Because now it will use the default values of [].

Hence when calling the post_process() function, it fails due to type mismatch. This now gives an error

restart;
foo:=proc(A::integer,{ic::`=`:=[]})
   print("in foo, A=",A, "ic=",ic);
   post_process(A,'new_ic'=ic);
end proc;

post_process:=proc(A::integer,{new_ic::`=`:= []})
    print("in postprocess, A=",A, "ic=",new_ic);
end proc;

foo(3)

Error, (in foo) invalid input: post_process expects value for keyword parameter new_ic to be of type `=`, but received []

So the way I do this now, is to add an extra check each time, like this

restart;
foo:=proc(A::integer,{ic::`=`:=[]})
   if nargs = 2 then #is ic passed in?     
      post_process(A,'new_ic'=ic);
   else
      post_process(A);
   fi;
end proc;

post_process:=proc(A::integer,{new_ic::`=`:= []})
    print("in postprocess, A=",A, "ic=",new_ic);
end proc;

foo(3)# now it works

But in my actual code, I have more than one keyword argument, and I have to keep checking for correct number of arguments each time, to know which arggument to pass along. 

So far, I did not find an easy way around this.

Any suggestion how to do this better? passing keyword argument with default values? from one function to another without getting into these problems?

Maple 2020.2

Dear All 

I would like to calculate the five first terms of a  polynomial  sequence

I wrote in maple 

sum(x^r*(sum((-1)^s*binomial(r, s)*pochhammer((a+s+1)*d, n), s = 0 .. r))/factorial(r), r = 0 .. n), n = 0 .. 4);

I obtained 

0,0,0,0,0

which seems to be false

where is the problem 

Best regards 

This simple set of integrations works correctly and quickly in Maple 17 and other releases, but not in Maple 2020.

psi(x) := (-1)^v*(alpha*GAMMA(k-v)/v!/GAMMA(k-2*v-1)/GAMMA(k-2*v))^(1/2)*exp(-1/2*k*exp(-alpha*x))*                 (k*exp(-alpha*x))^(1/2*k-v-1/2)*LaguerreL(v,k-2*v-1,k/exp(alpha*x))/binomial(k-v-1,v);

Int(eval(%, [k=30.5, v=j, alpha=2.5])^2, x=-1..infinity) =
   seq(evalf[12](Int(eval(%, [k=30.5, v=j, alpha=2.5])^2, x=-1..infinity)), j=0..5);

Every time that I try this simple integration in Maple 2020 I receive a message "kernel connection lost".  Why???

Hi there,

what's wrong with this example:

ph_ex.mw

?

Thank you