Plotting exponential curves with random numbers.

Ok I wonder if anyone can help me. Forgive me, but I am a complete novice with MATLAB and only ever had to complete worked examples in my class but now I have had this seemingly huge task put in my hands.

So I have some data that I have been able to plot as a scatter and (as I couldn't figure out how) through excel, have got the equation of the line which roughly resembles an exponential curve (as per the conditions of the question) as y= b*e^(c*x) ==> y=0.0274*exp(0.0332*x).

I now need to generate 100 further exponential lines to be displayed on the same graph using a random number function where b and c are changing.

I'm really not sure how to get this started.

b needs to exist between 0.15 and 0.424 c needs to exist between 0.252 and 0.372

I'm not sure how to get the random number thing working or how I can plot 100 lines on one graph.

Any help anyone could give would be greatly appreciated.

Answer 1

[Mischa Kim]

This will do:

N = 100;
b = 0.150 + (0.424-0.150)*rand(N,1);
c = 0.252 + (0.372-0.252)*rand(N,1);

x = 0:0.1:10;

figure
box; grid;
hold all
for ii = 1:N
    y = b(ii)*exp(c(ii)*x);
    plot(x,y)
end

rand(N,1) generates a 100-by-1 vector of uniformly distributed pseudorandom numbers. The loop will take care of displaying all 100 curves, which you can plot all in one figure by using the hold all command.

[Liam]

Thanks very much!

Answer 2

[Jos (10584)]

Here is something to get you started

x = linspace(-10,10,100) ;

hold on   % help!
for k = 1:5,
  B = 0.15 + (0.424-0.15) * rand(1,1) ;
  C = … % do it yourself, given the equation for B
  y = B * exp(C * x) ;
  plot(x,y,'-') % plot a line
end
hold off