CODEWITHSUNDEEP
matlab
user2791484
user2791484

Reputation: 61

vector as function's input in matlab?

i'd like to Write a function that receives a 2x1 matrix cointaining the x and y.(no scalar inputs) is it possible? I tried as below:

function [d] = dist(A,B)

d=sqrt(((A(1)-B(1))^2+(A(2)-B(2))^2));
end

A and B are 2*1 matrices . how to put vector as function's input??

Upvotes: 0

Views: 28731

Answers (2)

Dan
Dan

Reputation: 45752

I have a different interpretation of your question, I think you're asking how to make your function output all the distances for two lists of (x,y) coords? If so then like this:

function [d] = Dist(A,B)
    d=sqrt(((A(:,1)-B(:,1)).^2+(A(:,2)-B(:,2)).^2));
end

So you need to change your ^ from a matrix operation to an elementwise vector operation .^ and then you need to access the first column but ALL the rows i.e. (1,:)

e.g.

A = [0,0;
     0,1;
     1,1]
B = [1,1;
     1,1;
     1,1]

Dist(A,B)

ans =

   1.41421
   1.00000
   0.00000

By the way you could neaten up this function like this and still get the same result:

function [d] = Dist(A,B)
    d=sqrt(sum((A-B).^2,2));
end

Upvotes: 1

Floris
Floris

Reputation: 46375

If you want to pass two vectors (since you have A and B each having two elements) as a single parameter, you can either create a 2x2 matrix or a 4x1 vector to pass in. Or you can decide to pass in a cell array (which gives you a bit more flexibility). Example:

A = [1 2];
B = [4 5];

C = [A; B];

d = myDistance(C);

function m = myDistance(x)
  dxy = diff(x); % do both x(2,1) - x(1,1) and x(2,2) - x(1,2) in one operation
  m = sqrt(sum(dxy.^2));

Alternatively, passing A and B as two separate parameters (which makes a lot of sense from readability) should work in the way you described in your question...

Upvotes: 1

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