Hello, I have a problem with a system of ODEs. The three differential equations are as follows: diff(c(t),t) = 2*(c(t))^2 + 21/50*c(t) - 1/100*(h(t))^2 - 1/5*c(t)*h(t) - (9/2000)*h(t) + 49/4000; diff(h(t),t) = h(t)*(c(t) - 1/5*(h(t)-1)); diff(k(t),t) = 8/100*k(t) - h(t) - 1/5*k(t)*h(t); diff(c(t),t) = 2*(c(t))^2 + 21/50*c(t) - 1/100*(h(t))^2 - 1/5*c(t)*h(t) - (9/2000)*h(t) + 49/4000; diff(h(t),t) = h(t)*(c(t) - 1/5*(h(t)-1)); diff(k(t),t) = 8/100*k(t) - h(t) - 1/5*k(t)*h(t); As t goes to infinity the three variables c(t), h(t), k(t), respectively, approach certain values -in this setting 1/50, 11/10, 55/3, respectively- with the values of the derivatives converging to 0. (The point is saddle path-stable.)

Hi all, I am just curious about this problem, which has been in my mind for long time. I have seen some complex-valued functions, which are not in closed-form. For example, the complex-valued functions are defined by ODE: y'(t)=a+b*y(t)+c*(y(t))^2 + ... where the numbers in above ODE are complex-valued and the complex-valued functions are defined by functions of y(t), such as exp(y(t)), etc. Such ODEs can only be solved numerically. Sometimes even a closed-form solution is available, we would rather choose to solve it numerically because the closed-form solution often involves hyper functions and super complicated expressions.

I have the following:

>                 /             /         2          \\    
>              1  | 2    2      |/ 2    2\       2  2||    
>       eqn := - +\b  + a , sqrt\\b  + a /  - 4 a  c // - c
>              2                                           
                                                     (1/2)    
        1  2   1  2   1 / 4      2  2    4      2  2\         
 eqn := - b  + - a  + - \b  + 2 b  a  + a  - 4 a  c /      - c
        2      2      2                                       
>                          solve(eqn, c)
                               2    2

Here are some possible bugs or limitations that I have come across while working with Tensors in the new physics package. I have done best of my efforts looking into the documentation, but it is still possible that the bugs I am listing are not bugs at all but outcome of lack of my knowledge in using Maple. My intention of creating this blog is to not to criticize but to help the Physics package development team in making updates. I appreciate their efforts for developing a much needed package for areas like fluid mechanics, continuum mechanics, theory relativity etc. Platform I am using: Maple Ver 11.01 on Mac OS X 10.4.10

Here's a question I was asked very recently: "When creating a plot, is it possible to specify the points at which the input expression should be evaluated?" The answer is "yes" for 2-D plots, and this is done with the 'sample' option. Use the command plot(f(x), x=a..b, sample=[x1, x2, ..., xn]) to have f(x) evaluated at points x1, x2, ..., xn. Note this produces a plot that includes points with x-values x1, x2, ..., xn. To produce a plot that contains only these points, you need to add the adaptive=false option as well.

I want to solve the following task efficiently. I need to read data from S files (in my case S = 50000). Each file has T rows of 5 floats each. Here T=1000 is a time index and 5 is the dimension of a dynamical system. From each file I want to read the j coordinate and to assign its T values to a column in a matrix X. At the end of this process I'll have an X array or matrix of dimension T x S. How can I do this efficiently? When I use 'readdata' in order to read the Tx5 matrix from a single file into a list D, this is a fast process. But assigning, naively, the j column from this matrix to my matrix X, using a for loop,

Hi, I am Er. Vishal Jain new to maple prime. I need help in developing dynamic 2D-graphs(pi-chart, conic section etc.) in .mw and respectively shade the graph.

The first example below seems OK. But, should I be expecting the different behaviour in the second example?


> restart:
> p := module() option package; export foo;
> foo:=proc(x) x; end proc;
> end module:

> foo := proc(x) cos(x); end proc:

> foo(3.2);
-0.9982947758

> p:-foo(3.2);
3.2

> evalhf(p:-foo(3.2)); # OK
3.20000000000000018

> restart:
> p := module() option package; export sin;

While posting an initial question is not problematic, when editing or adding a comment thereafter, one is presented with a box in which to compose that is partially concealed by content at the right of the screen, e.g., Active forum topics and Recent comments. One can continue to type behind the veil and have it display fine in the preview, but this seems anomalous. I have noted it on two different computers. Do others have this problem? Is there a way to work around this besides truncating ones sentences with early returns?

As per instructions at the bottom of page 217 of the user manual, I wish to alter the y-axis range of a 2D plot. The instructions say to right click the plot region. Select axes and then range, however, doing so allows one to select axes, but the menu item range is nowhere to be found in the menu as described by the manual. The menu only offers the choices of normal, boxed, framed, none, properties, labels, toggle gridlines, and set gridline properties.

My old Mathcad 7 had a snap to function that allowed one to trace a given plot. Using the point probe on Maple does not seem to have an equivalent feature. If one wants to know a particular x y location, one must hover the point probe over the desired spot, but this is not ideal as it it very sensitive to movement. Is there a snap to feature for tracing plots? If so, how is is activated?

im new so excuse the relavie easy ness of this question. i typed >plot(1/7-5*(sin(x)),-10..10,-10..10); then 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 and an empty graph comes up i looked on the help page but i dont really understand it, i was hoping mapleprimes can help??? once again sorry for the easyness of the question!!!

Hi I am trying to combine a previous, numerically obtained result in a subsequent calculation: outline: suppose i have a given function, f(x), and i wish to construct the following boundary value problem: y''(x)=f(x), y(0)=1, y(1)=2 the known function f(x) is a result of another calculation, which i have obtained numerically. (f(x)=proc(x)...end proc, or something to that affect). code: -------------------------------------------- > restart; > sys := {diff(y(x), x) = x, y(0) = 1}; / d \ { --- y(x) = x, y(0) = 1 }

How can I create the inert form of the following function: dm:=z->diff(z,t)+v[c]*d_[c](z); Note d_ is the new indicial differential operator available in physics package of Maple 11. Its inert form is %d_. What I need is that when I write, dm(rho), maple does not expand it into two terms using the above function, but displays the compact form dm(rho). I want to see the expanded form, only when needed, not at every step where dm is used. So at other steps, I just want to see dm(rho), without evaluation. Thanks, Pawan Takhar

In the example below, the plot option axesfont affects both axes in Maple 10.06, but in Maple 11.01 it affects only the vertical axis. Is this a feature, or a bug? If it’s a feature, how can I change the font of the horizontal axis tickmarks?

restart;
dates := [0 = "21/8/00", 140 = "8/1/01", 536 = "8/2/02", 885 = "23/1/03", 1267 = "9/2/04", 1628 = "4/2/05", 2004 = "15/2/06", 2200 = "30/8/06", 2479 = "5/6/07", 2531 = "27/7/07"];
xy := [[0, 2.5], [140, 2.2], [536, 2.6], [885, 2.5], [1267, 3.3], [1628, 3.1], [2004, 5.0], [2200, 3.0], [2479, 5.9], [2531, 4.3]];
plots[pointplot](xy,symbol=circle,tickmarks=[dates,default],axesfont=[TIMES,ROMAN,8]);