Mr. Robert Long

## 1399 Reputation

13 years, 9 days
Leeds, United Kingdom
Business Consultant Data Scientist Statistician

## jacobian of system of ODEs...

Maple
Greetings Is there a nice way to obtain the jacobian of a system of ODEs ? For example with restart: ross_x:=diff(x(t),t)=-y(t)-z(t): ross_y:=diff(y(t),t)=x(t)+a*y(t): ross_z:=diff(z(t),t)=b+x(t)*z(t)-c*z(t): rossler_sys:=ross_x,ross_y,ross_z; I can't seem to find an easy way to do it, other than re-write the system altogether s_x:=-y-z: s_y:=x + a*y: s_z:=b+z*(x-c): J:=Matrix([[diff(s_x,x),diff(s_x,y),diff(s_x,z)],[diff(s_y,x),diff(s_y,y),diff(s_y,z)],[diff(s_z,x),diff(s_z,y),diff(s_z,z)]]); .....which seems horrible. Thanks LR

Maple
Greetings

## function vs procedure...

Maple
Hi all I see it is very easy to define a simple function in Maple using -> But what if more than a single expression is needed and if local variables are needed ? Is there a way to put several statements and use local variables in a function definition ? For example to define a function that takes a list as it's argument and returns the arithmetic mean or the simple sum. Must such things be done with a procedure ? Thanks !

## cannot change horizontal range on plot...

Maple
Hi all I have > tst:=-(1-cos(p))/p^2+1/2*cos(1/4*p)^2*cos(1/8*p)^2*cos(1/16*p)^2: >plot(tst); which seems to work OK. However, this generates an error plot(tst,Pi..2*Pi); Warning, unable to evaluate the function to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct Plotting error, empty plot ...as does any other range I have tried. I guess it's something very simple, but if someone can point me in the right direction I would appreciate it !

## Worksheet causing maple to crash...

Maple
I'm very new to maple and I've been experiencing a few difficulties. One in particular is quite frustrating: when opening a worksheet in classic worksheet mode I get a message that it was created in an earlier version, and after clicking OK maple crashes. For example, with the document here: http://www.maplesoft.com/applications/view.aspx?SID=1404 I am using Maple 12. This problem does not occur in standard gui mode, only classic worksheet mode but for a variety of reasons I wish to use classic as much as possible. Thanks
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