## Set up an OR argument for equation

### Grant Murdoch (view profile)

on 18 Mar 2019
Latest activity Answered by Jos (10584)

on 18 Mar 2019

### Torsten (view profile)

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.

### Torsten (view profile)

on 18 Mar 2019
Edited by Torsten

### Torsten (view profile)

on 18 Mar 2019

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

### Jos (10584) (view profile)

on 18 Mar 2019

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)