Set up an OR argument for equation

I am using Matlab to simulate the pounding bwtween structures during earthquake events.

To do this the equation for the pounding force, F, must change depending on the output of another parameter. The conditions are:

F(t) = k*s + c*v(t) when v(t) > 0

F(t) = k*s when v(t) < 0

What is the best way to set this up?

The code for both the equations above is:

fp = (k_inp*(x1-x2-gap)+c_inp*(xdot_1-xdot_2)).*(sign(x1-x2-gap)+1)/2 when v(t) > 0

fp = (k_inp*(x1-x2-gap) when v(t) < 0

where v(t) = (xdot_1-xdot_2)).*(sign(x1-x2-gap)+1)/2

Thanks in advance for any replies.

Answer 1

[Torsten]

v = (xdot_1-xdot_2)).*(sign(x1-x2-gap)+1)/2;
if v > 0
  fp = (k_inp*(x1-x2-gap)+c_inp*(xdot_1-xdot_2)).*(sign(x1-x2-gap)+1)/2 
else
  fp = k_inp*(x1-x2-gap) 
end

Answer 2

[Jos (10584)]

Can't you use logical indexing? A simplified example

v = 10:20
q = v > 13 & v < 18 
f(q) = 2*v(q) 
f(~q) = 30 + v(q) 

Answer 3

[Jos (10584)]

Simpler, without an if-else:

v = (xdot_1-xdot_2)).*(sign(x1-x2-gap)+1)/2;
fp = (k_inp*(x1-x2-gap) + (v>0) * c_inp * (xdot_1-xdot_2)).*(sign(x1-x2-gap)+1)/2 
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