Using linprog for equation with exponential and upper limit
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Orongo
el 15 de Feb. de 2018
Comentada: Walter Roberson
el 16 de Feb. de 2018
Hi, I am replicating a calculation done in Excel that set up the equation mu(x) accordingly
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/170380/image.png)
Excel uses Solver nonlinear GRG, and I'm thinking of using Matlab's function linprog to replicate this. The unknown parameters are a, b and c, where x represent the age. I understand the from the web that x=linprog(f,A,b) and struggle to understand what f and A should be in my program. I follow the first vector of elements in A should be ones, but that is as far as I get. Please advise.
Many thanks.
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Birdman
el 15 de Feb. de 2018
These looks like a piecewise function and can easily be replicated by MATLAB's piecewise function(requires Symbolic Toolbox):
syms a b c x
mu(x)=piecewise(x<=100,a+b*exp(c*x),x>100,a+b*exp(c*100)+(x-100)*0.01)
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Walter Roberson
el 16 de Feb. de 2018
This will not work with linprog(). linprog() accepts a vector of coefficients, not a function.
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Walter Roberson
el 15 de Feb. de 2018
Your function is nonlinear in c and x. You cannot use linprog for this. linprog is strictly for linear functions.
If you did not have the a + portion of the expression then you could potentially have used a log transform, log(b) + c*log(x) which is linear in log(x)... But that will not work with the a+ portion of the expression being there.
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