How to use vectors in conditional functions?
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I have a function which accepts four numbers:
function [ force, stiff ] = myfunction( d_a, d_b, v_a, v_b)
After running my function I want to display a surf plot by putting 4 vectors through the function and then plotting.
In the function myfunction, when I introduce conditions (e.g. if, &&, ==) the function does not work. How can I get around this problem?
4 Comments
Walter Roberson
on 22 Jul 2011
When you have vectors, you need to use | and & instead of || and && .
However, those will generate vectors of logical values. If you want to make decisions based upon the individual logical values, you need to loop or you need to use logical indexing. With a vector of logical values, you can use all() or any() if what you care about is the group behavior of the vector of values.
Accepted Answer
Paulo Silva
on 20 Jul 2011
For John's example code:
idx=a>1 & a<3 %mark the index values where your condition is true
idx1=a>2 %mark the index values where your second condition is true
c=a(idx)+a(idx1)*2
6 Comments
More Answers (2)
Daniel Shub
on 6 Jul 2011
Without any more information regarding what doesn't work, I am just guessing ...
The == operator with a scalar returns a scalar, with an array it returns an array. You may want to replace
x == y
with
any(x == y)
or
all(x == y)
you may also want to replace && with just & and with |.
0 Comments
John
on 20 Jul 2011
1 Comment
Walter Roberson
on 20 Jul 2011
John, if "a" is in the range of being greater than 2 and less than 3, then that satisfies a>1 & a<3, so b=1 would be appropriate for that case according to your code. But then you have the "elseif" for a>2 : are you sure that for the range (2,3) you want b=1 and not the b=2 of the elseif ? Otherwise you might as well (for the vector case) use
if a>1 && a<3
b = 1;
elseif a>=3
b = 2;
end
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