MaplePrimes - answers and comments on Question, Plotting Values from a Loop

Some possibilities

Scott03 — Mon, 01 Mar 2010 20:22:12 Z

If you want to do with your for loop you could do something like the following

> result:=[]:
> for i from 0 to 25 do assign('result',[op(result),[i,evalf(eval(eq2,t=i))]]) end do:

Now to plot these results you can just call

> plots:-pointplot(result);

You may also find that the for loop isn't the most effecient for all your tasks, for example you could use the seq command to do the same thing in this way

> result:= [seq([i,evalf(eval(eq2,t=i))], i=0..25)];
> plots:-pointplot(result);

Since you have such a small number of points you are evaluating at, you may not notice too much of an improvement, but as you get to a larger number of points you may want to try this.

Scott
Application Developer
Maplesoft

Good ideas

contact_petersen — Mon, 01 Mar 2010 22:23:45 Z

The seq command you suggested is a better way of displaying the data, so thanks.

However i still cant figure out how to draw a graph of n(t) vs t. What commands should i be using

pointplot

Scott03 — Tue, 02 Mar 2010 00:20:30 Z

How do you want this graph to look like? The plots:-pointplot command will take the list of points (which is your n(t) vs t) and output the points on the plot. If you want to connect a line between the points, you can use the connect=true option.

Scott
Application Developer
Maplesoft

cant see whats wrong

contact_peterson — Wed, 10 Mar 2010 04:53:35 Z

It seems not to want to plot the values i cant tell what i have done wrong. Heres the entire document. > eq1 := diff(n(t), t)+lambda*n(t) = 0; / d \ |--- n(t)| + lambda n(t) = 0 \ dt / > eq2 := dsolve([subs(lambda = .1, eq1), n(0) = 10]); / 1 \ n(t) = 10 exp|- -- t| \ 10 / > f(i) :=evalf(eval(eq2,t=i)); i -> evalf(eval(eq2, t = i)) > result := seq([i, f(i)], i = 0 .. 25); [0, n(0) = 10.], [1, n(1) = 9.048374180], [2, n(2) = 8.187307531], [3, n(3) = 7.408182207], [4, n(4) = 6.703200460], [5, n(5) = 6.065306597], [6, n(6) = 5.488116361], [7, n(7) = 4.965853038], [8, n(8) = 4.493289641], [9, n(9) = 4.065696597], [10, n(10) = 3.678794412], [11, n(11) = 3.328710837], [12, n(12) = 3.011942119], [13, n(13) = 2.725317930], [14, n(14) = 2.465969639], [15, n(15) = 2.231301601], [16, n(16) = 2.018965180], [17, n(17) = 1.826835241], [18, n(18) = 1.652988882], [19, n(19) = 1.495686192], [20, n(20) = 1.353352832], [21, n(21) = 1.224564283], [22, n(22) = 1.108031584], [23, n(23) = 1.002588437], [24, n(24) = 0.9071795329], [25, n(25) = 0.8208499862] > with(plots); > pointplot(result); Error, (in plots/pointplot) incorrect first argument >

yes

contact_peterson — Wed, 10 Mar 2010 07:04:51 Z

that has solved the first argument problem, however i must still have made a mistake somewhere because it still doesnt want to plot, what am i doing wrong. > points := seq([i, rhs(f(i))], i = 0 .. 25); [0, 10.], [1, 9.048374180], [2, 8.187307531], [3, 7.408182207], [4, 6.703200460], [5, 6.065306597], [6, 5.488116361], [7, 4.965853038], [8, 4.493289641], [9, 4.065696597], [10, 3.678794412], [11, 3.328710837], [12, 3.011942119], [13, 2.725317930], [14, 2.465969639], [15, 2.231301601], [16, 2.018965180], [17, 1.826835241], [18, 1.652988882], [19, 1.495686192], [20, 1.353352832], [21, 1.224564283], [22, 1.108031584], [23, 1.002588437], [24, 0.9071795329], [25, 0.8208499862] > with(plots); > pointplot(points); Error, (in plot/options2d) unexpected options: [[3, 7.408182207], [4, 6.703200460], [5, 6.065306597], [6, 5.488116361], [7, 4.965853038], [8, 4.493289641], [9, 4.065696597], [10, 3.678794412], [11, 3.328710837], [12, 3.011942119], [13, 2.725317930], [14, 2.465969639], [15, 2.231301601], [16, 2.018965180], [17, 1.826835241], [18, 1.652988882], [19, 1.495686192], [20, 1.353352832], [21, 1.224564283], [22, 1.108031584], [23, 1.002588437], [24, .9071795329], [25, .8208499862]] >

yep

contact_peterson — Wed, 10 Mar 2010 21:15:32 Z

yes it was that simple, thanks everyone for helping me out. sorry for being such an idiot.