How to display the selected function from a switch case statement

Hi all,

I have a switch cases statement with selects the best in terms of RMSE fitting sinusoid function to my dataset. My question is how to display in the Command window the mathematical expression of the selected function. The code is like this.

function [RMSE,ltsc] = ltsc_scoref(A,data,period,fun)
%LTSC_SCOREF Long term seasonal component score function with square error. 
%   Written by Rafal Weron (2009.08.18)
%   Copyright (c) 2009 by Rafal Weron
N = length(data);
x = (1:N)'/period;
switch fun
    case 1      % sinusoid with linear trend
        ltsc = A(1).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x;
       % disp('A(1).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x')
    case 2      % sinusoid with cubic trend
        ltsc = A(1).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x + A(5)*x.^2;
        %disp('A(1).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x + A(5)*x.^2')
    case 3      % sinusoid with linear trend and linear amplitude
        ltsc= (A(1) + A(6)*x).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x;
        %disp('A(1) + A(6)*x).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x')
    case 4      % sinusoid with cubic trend and linear amplitude
        ltsc = (A(1) + A(6)*x).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x + A(5)*x.^2;
        %disp('(A(1) + A(6)*x).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x + A(5)*x.^2')
    case 5      % 2 sinusoids with cubic trend and linear amplitude
        ltsc = (A(1) + A(6)*x).*( sin( 2.*pi.*(x+A(2)) ) + sin( pi.*(x+A(2)) ) )+ A(3) + A(4)*x + A(5)*x.^2;
        %disp('(A(1) + A(6)*x).*( sin( 2.*pi.*(x+A(2)) ) + sin( pi.*(x+A(2)) ) )+ A(3) + A(4)*x + A(5)*x.^2')
end
% subtract level and compute score (sum of squared errors, SSE)
RMSE = ( mean( (abs(data - ltsc)).^2 ) )^0.5;
disp(sprintf('ltsc= %g', ltsc)); 
 end

What I would like to see is that if for example case 3 is selected: ltsc= (A(1) + A(6)*x).*sin( 2.*pi.*(x+A(2)) ) + A(3) + A(4)*x; Thanks

Answer 1

[John D'Errico]

Hint:

A= [2 3 5];
disp([num2str(A(1)),'.*X + ',num2str(A(2)),'.*Y + ',num2str(A(3))])
2.*X + 3.*Y + 5

The above is only a complete guess as to what you intend. Note that it can be pretty easily extended to a general case, where you write a small helper function that takes a list of terms and coefficients, then creates a string. With just a wee bit of effort, you can make it handle a general nonlinear case. But you need to decide how generally nonlinear a function you may have.

The point is, write a simple function that will take some functional form, with a coefficient or coefficients, returning a string. Then just loop over the terms, and build up a complete string of terms. (Not difficult, since I recall doing exactly this many years ago.)

As I said, only a guess though.

Answer 2

[Stephen23]

You can use func2str:

>> fun = @(x,y) sqrt(x) + sin(y);
>> str = func2str(fun)
str = @(x,y)sqrt(x)+sin(y)