Hello,

The point is in division, if you want do do everything elementwise (expression concerning every element of a vector t), pay attention the difference between / and ./ . These two are totally different operators.

y = (m*p) ./ (p + (m - p)*exp(-k*m*t));

Moreover, it is not advisable to use [ ] where you need ( )

Regards,
Radovan

On 1/4/2014 10:19 PM, Ryan M. Castle wrote:
Hello. I am new to scilab. I need to create a simple plot of the solution to 
the logistic equation and have been frustrated by scilab. The plot should be 
decaying, approaching 20 with an initial population of 300. Here is what I have 
(in .sce file):

clc
clear
p = 300;
m = 20;
k = .1;
t = [0:.01:5];

y = (m*p)/[p + (m - p)*exp(-k*m*t)];

plot(t, y, 'LineWidth',3)
xlabel('t'),ylabel('y');


If I define just  t=0 then I get correct result of 300. If I have t=5 I get 
(close to) 20. All good.

But when I plot t=0:.01:5; I get a plot that is 1) increasing not decreasing 
and 2) the initial and limiting values are all wrong, just a fraction of 
correct values.

What am I missing? Such a simple plot...
Thank you.
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