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arraysmatlab
Andrew
Andrew

Reputation: 31

Creating an array of a single value

I'm using matlab and want to check whether a column vector is equal to another withing 3dp, to do this i'm trying to create an array full of 0.001 and checking whether it is greater than or equal. is there a simpler way than a for loop to create this array or no?

Upvotes: 3

Views: 15668

Answers (4)

Kena
Kena

Reputation: 6921

is there a simpler way than a for loop to create this array or no?

Yes, use

ones(size, 1) * myValue

For instance 

>> ones(5,1)*123

ans =

   123
   123
   123
   123
   123

Upvotes: 10

rlbond
rlbond

Reputation: 67849

So, let me know if this is correct.

You have 2 vectors, a and b, each with N elements. You want to check if, for each i<=N, abs(a(i)-b(i)) <= 0.001.

If this is correct, you want:

vector_match = all(abs(a-b) <= 0.001);

vector_match is a boolean.

Upvotes: 4

Amro
Amro

Reputation: 124563

Example:

a = rand(1000,1);
b = rand(1000,1);

idx = ( abs(a-b) < 0.001 );
[a(idx) b(idx)]

» ans =
       0.2377      0.23804
       0.0563     0.056611
      0.01122     0.011637
        0.676       0.6765
      0.61372      0.61274
      0.87062      0.87125

Upvotes: 1

Noon Silk
Noon Silk

Reputation: 55172

You may consider the 'find' command, like:

a = [ 0.005, -0.003 ];
x = find(a > 0.001);

FWIW, I've found comparing numbers in MATLAB to be an absolute nightmare, but I am also only new to it. The point is, you may have floating-point comparision issues when do you the compares, so keep this in mind when attempting anything (and someone please correct me if I'm wrong on this or there is a beautiful workaround.)

Upvotes: 0

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