Asymptotes and exponential decay functions

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Lynn Knoblauch 2012-6-30

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https://ww2.mathworks.cn/matlabcentral/answers/42425-asymptotes-and-exponential-decay-functions

Does anyone know how to write a script for an exp decay and get the asymptote value as well?

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Walter Roberson 2012-6-30

Which asymptote? Substitute +inf or -inf for "t" to get those asymptote. Asymptote near a singularity is more difficult.

Lynn Knoblauch 2012-6-30

编辑：Walter Roberson 2012-6-30

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Thank you for your response. I am VERY novice at this. I may be confused/ wondering if the estimates for the y axis intercept are calculated as the the y-intercept minus asymptote. But I think I need an entirely different code for this. Right now I am working with:

time = [0.009 0.01 0.012 0.0150 0.0167 0.02 0.023 ];
SWA = [11 10 9 8 7.5 7.1 6.9 ];
    %set up exp equation
    expdecay = @(EXD,xx)(EXD(1)*exp(-EXD(2)*xx));
    %initial value cross
    EXD = [SWA(1) 2];
    %nlinfit to calc EXD(1) and EXD(2) in fitting
    expfit = nlinfit(time,SWA,expdecay, EXD) 
hrfit = min(time):0.001:max(time);
swafit = expdecay(expfit,hrfit);
figure(1)
plot(time,SWA,'ok','markerfacecolor','m','markersize',5)
hold on
plot(hrfit,swafit,':x')
hold off
xlabel('time across night')
ylabel('SWA')