# Expression (equation)

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Jan on 8 Dec 2011
Hello, how to define an expression, for example 1-e^(-At) where I can define and change parameters A and t and than figure changes of the curve in a graph.
Thanks
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### Accepted Answer

Paulo Silva on 8 Dec 2011
Simplest version I can think of
t=0:0.1:100; % Time vector
A=0.1; % Value of A that you can change
plot(t,1-exp(-A(n)*t)) % Represent it on a figure
If you place the cursor on the value of A you can try several values using the Editor tools (look on the tools of your editor window - 1.0 + ... press those symbols and the script runs with a new value for A)
Just for fun here's a version using subplots
clf
t=0:0.1:10;
A=[0.01 0.1 0 1];
for n=1:4
subplot(2,2,n)
plot(t,1-exp(-A(n)*t))
title(['A=' num2str(A(n))])
end
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Jan on 8 Dec 2011
thx :)

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### More Answers (1)

Sean de Wolski on 8 Dec 2011
And to add on to Paulo's example:
t=0:0.1:100; % Time vector
A=0.1;
y = 1-exp(-A*t); % Value of A that you can change
H = figure;
plot(t,y)
linkdata(H,'on');
shg;
pause(2) %watch the magic in 2 seconds
A = .8;
y = 1-exp(-A*t);
if you want it to automagically update when you change A or y.
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Jan on 8 Dec 2011
Is it possible to model it in the Simulink?

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