move regression code from statistics to regression folder

regression/code/boltzmann.m

@@ -0,0 +1,7 @@
+function y = boltzmann(parameter, x)
+% parameter 1: alpha
+% parameter 2: k
+% parameter 3: x_0
+% parameter 4: y_0
+
+y = (parameter(1) ./ (1 + exp(-parameter(2) .* (x - parameter(3))))) + parameter(4);

regression/code/create_linear_data.m

@@ -0,0 +1,7 @@
+function y = create_linear_data(x)
+
+m = 2.5;
+n = -0.35;
+d = 2.5;
+
+y = x .* m + n + randn(size(x)) .* d;

regression/code/estimate_regression.m

@@ -0,0 +1,7 @@
+function param = estimate_regression(x,y,p_0)
+
+objective_function = @(p)lsq_error(p, x, y);
+param = fminunc(objective_function, p_0);
+disp(param)
+param1 = fminsearch(objective_function, p_0);
+disp(param1)

regression/code/exponential.m

@@ -0,0 +1,5 @@
+function y = exponential(parameter, x)
+% Function implements an exponential function with two parameters
+% controlling the amplitude and the time constant.
+
+y = parameter(1) .* exp(x./parameter(2));