## 140 Reputation

14 years, 218 days

## lower-right convex hull of a set of poin...

Maple 15

Hi!,

Assume that we hace a set points in the plane, put X:=[a1,a2,...,aN] where each ai is given by its coordinates [x,y]. The commnad "convexhull(X)" give us the points of the convex hull of X, but how I can find to "lower-right" of these points? Please, see the attached image. I need to findo the points A,C,E and F, marked with a solid circle.

## From Mathematica to Maple...

Maple 2015

Dears,

I have seen a Mathematica code which I would like to have it in Maple, since I do not know that program. Let f(z) an analytic function, say f(z):=1+2^{z+1}+3^{z}. To find the roots of f(z) in a regingion, we can use in Maple the command "Analytic" (of the package "RootFinding"). However, in Mathematica is used the following:

L = 20; Monitor[zeros = Flatten@Table[N[z /. Solve[f[z] ⩵ 0 && k L ≤ Re[z] ≤ k L + L && -10 < Im[z] < 10, z], 25],{k, 300}],k];

What means the "N[z/. Solve..." instruction? Also, the following command:

SortBy[zeros, Re];

Can be "translated" to Maple?

With Regards,

G.

## Convert Peano curve into a function...

Maple 15

Hi!

I have seen th following procedure to compute the image of the points of [0,1] under the so called Peano space-filling curve (sorry, I have to pasted the code in "text plane" mode):

P[0] := (x, y) -> ((1/3)*y, (1/3)*x);

P[1] := (x, y) -> (-(1/3)*x+1/3, (1/3)*y+1/3);

P[2] := (x, y) -> ((1/3)*x, (1/3)*y+2/3);

P[3] := (x, y) -> ((1/3)*x+1/3, -(1/3)*y+1);

P[4] := (x, y) -> (2/3-(1/3)*y, 2/3-(1/3)*x);

P[5] := (x, y) -> ( (1/3)*x+1/3, 1/3-(1/3)*y));

P[6] := (x, y) -> (1/3)*x+2/3, (1/3)*y);

P[7] := (x, y) -> (-(1/3)*x+1, (1/3)*y+1/3);

P[8] := (x, y) -> ((1/3)*x+2/3, (1/3)*y+2/3);

peano := proc (t::numeric, depth::integer)

local q, r; global P;

if depth = 0 then return 0, 0 end if;

q := floor(9*t); r := 9*t-q;

return P[q](peano(r, depth-1))

end proc;

Now, I need to use the procedure "peanofun" as a function. For instance, if we define f:=(x,y)->x+y, I need to use (plot, compute, etc) for instance, the function f(peanofun(t,5))

Can you help me with this issue, please?

## Error with Analytic()...

Maple 15

Hi!

I am an error with the use of the function "Analytic" of the packpage RootFinding. These are the procedures:

CreaCos := proc (C, n, m, t) local k, F; F := C[1][1]+(C[1][2]-C[1][1])*t; for k to n-1 do F := F, C[k+1][1]+((1/2)*C[k+1][2]-(1/2)*C[k+1][1])*(1-cos(Pi*m^k*t)) end do; return F end proc;

Then, for k=50, 100, 150... the instruction

works correctly. However, for higher values of k (for instance, k=250) returns the below error. Some idea or suggets about occurs this error?

Error, (in RootFinding:-Analytic) unable to evaluate `@`(evalf, proc (x) option remember; table( [( 0.524900000000000000000000000000e-1+Float(undefined)*I ) = Float(undefined)+Float(undefined)*I ] ) 31250*Pi*sin(62500*Pi*x)/(7/18-(1/2)*cos(62500*Pi*x)) end proc) at the value 0.524900000000000000000000000000e-1+Float(undefined)*I. The expression to be solved was probably not analytic.

## Functions defined by a procedure...

Maple 15

Hi,

Let, fixed an integer i and 1<=j<=2^{i}-1, for each x and y in [0,1] let the following mapping

Then, with the above procedure we can obtained, for a fixed i, all the mappings for j=1,...,2^{i}-1

However, How can I to evalute the "components" of the above procedure? For instance, I can not to compute CreaF(2)[1](0.35,0.465) (i.e., the first function in the "vector" CreaF(2), in x=0.35, y=0.465).

Thanks very much for your time.

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