if statement gives wrong results or does not work?

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I've got the following if statement within a for loop. In the beggining, i thought it's quite straight forward. I've got a scalar and an array, I have to compare each value of the array with that scalar and after that, to make certain calculations.
a_sat = -1.2;
a = [-5 -2 -7 0 -1 3 5];
for i = 1:length(a)
if a(1:length(a) ) >=a_sat
b = 0.45;
else if a(1:length(a)) < a_sat
b(i) = 3.*a;
This gives an undefined value of b. If I try to remove the counter in the if's, then I get a wrong result for the value of b. can anyone please help me with that? Thank you!

Accepted Answer

Iain on 15 Jul 2013
"any" and "all" are your friends,
You have actually written
if ALL of a >= a_sat
set "b"
else, if ALL of a < sat
set "b"
else % (i.e. some of a > sat and some < sat)
do nothing
I don't know what you're actually wanting.
I suspect what you want is something like this
if a(i) > a_sat % if just the "ith" part of a is > a_sat
b = 0.45; % set b to "max"
else %if not...
b = 3*a(i); % b = 3* the "ith" part of a.
Iain on 5 Sep 2014
If result is a matrix, when you take the min, you get a row vector. For that to go into the "then" part of the if statement, the ENTIRE row vector needs to be less than or equal to -0.005.

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