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MathGroup Archive 2007

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Re: NDSolve, Loop, Table, Plot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77662] Re: NDSolve, Loop, Table, Plot
  • From: dh <dh at metrohm.ch>
  • Date: Thu, 14 Jun 2007 05:38:42 -0400 (EDT)
  • References: <f4olu9$7as$1@smc.vnet.net>


Hi Solver

the variable p2 does not have a value. Presumably you wanted to write 

p2=0.1 instead of p1=0.1.

If you are using version 6 you must additionally wrap the Plot statement 

in a Print statement.

hope this helps, Daniel



Solver wrote:

> Hi,

> 

> I have a system of 3 differential equations and I would like to

> numerically solve them for different values of one parameter (e.g., p1

> = 0.5, 0.6, 0.7, 0.8, etc). Then, I want to 1) make a table for the

> results of B0[200], B1[200], and B2[200] for all values of p1 and 2)

> make plots of B0, B1, B2 through time for the different values of p1.

> Below is the code I tried. The table seems to work sometimes but when

> I run the code multiple times, the output is the same for all values

> of p1 (i.e., {{3.99315, 3.99315, 3.99315, 3.99315, 3.99315, 3.99315},

> {

>     0.0813405, 0.0813405, 0.0813405, 0.0813405, 0.0813405,

>    0.0813405}, {0.021349, 0.021349, 0.021349, 0.021349, 0.021349,

> 0.021349}}. I don't understand why?

> The Plot function gives me multiple plots but they are always the

> same, so it is not drawing plots for the different values of p1.

> 

> J = 1;

> r0 = 0.2;

> r1 = 0.2;

> r2 = 0.2;

> p1 = 0.1;

> 

> dB0 = J - r0*B0[t] - B0[t]*B1[t];

> dB1 = p1*B0[t]*B1[t] - r1*B1[t] - B1[t]*B2[t];

> dB2 = p2*B1[t]*B2[t] - r2*B2[t];

> 

> A = Flatten[Map[({B0[200], B1[200], B2[200]} /. # ) &,

> sol = Table[NDSolve[{B0'[t] == dB0, B1'[t] == dB1, B2'[t] == dB2,

> B0[0] == 1, B1[0] == 1, B2[0] == 1}, {B0, B1, B2},

> {t, 0, 200}], {p1, 0.5, 1, 0.1}]], 1] // Transpose

> Export["A.csv", A];

> Do[Plot[Evaluate[{B0[t], B1[t], B2[t]} /. sol, {t, 0, 200}, PlotStyle -

> {{RGBColor[1, 0, 0]}, {RGBColor[0, 1, 0]}, {RGBColor[0, 0, 1]}}]],

> {p1, 0.5, 1, 0.1}]

> 

> Thanks!

> 

> 




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