Huber function matlab plotting with two intervals

Hello,

I was trying to write this simple matlab function:

rho(eps)=0.5*eps^2 for eps<=k
rho(eps)=k*eps-0.5*k^2 for eps>k

for k=1.345

so my solution was:

k=1.345;

for eps=0:0.001:6
if eps<=k
    f1=0.5*(eps^2);
else
    f1=k*eps-0.5*(k^2);
end %if loop

end %for loop

plot(eps,f1)

There was almost empty graph and sometimes only linear function although this function is supposed to be nonlinear in the first part and linear in the other part.

and also i'm supposed to plot the derivative of this function after this is complete.

Answer 1

[Torsten]

k=1.345;
eps=zeros(6001);
f1=zeros(6001);
for i=1:6001
eps(i)=(i-1)*0.001;
if eps(i)<=k 
f1(i)=0.5*(eps(i)^2); 
else 
f1(i)=k*eps(i)-0.5*(k^2); 
end %if loop
end;
plot(eps,f1)

Best wishes

Torsten.

Answer 2

[Kentman]

Is there a way to plot the derivation of this function directly by matlab or we need to do it by hand then apply the result?

Answer 3

[Torsten]

Or more "MATLAB-like":

k=1.345;
eps=0:0.001:6;
f1=zeros(size(eps));
epsf=eps<=k;
f1(epsf)=0.5*eps(epsf).^2;
epsf=eps>k;
f1(epsf)=k*eps(epsf)-0.5*k^2;
plot(eps,f1);

Best wishes

Torsten.

Answer 4

[Kentman]

so the final matlab will be

clear all;close all;clc;

k=1.345; eps=zeros(6001); f1=zeros(6001); f2=zeros(6001); for i=1:6001 eps(i)=(i-1)*0.001; if eps(i)<=k f1(i)=0.5*(eps(i)^2); f2(i)=eps(i); else f1(i)=k*eps(i)-0.5*(k^2); f2(i)=k; end %if loop end; %for loop

plot(eps,f1,'k-') hold on plot(eps,f2,'b-')