A function with 2 inputs, how to make it accept a 2-by-1 array as an input?

Hi all,

There are some functions which accepts 2 inputs, such as inpolygon. For example:

K>> xv
xv =
     1
     2
     2
     1
K>> yv
yv =
     1
     1
     2
     2
K>> x = 1.5
x =
  1.5000
K>> y = 1.5
y =
  1.5000
K>> inpolygon(x, y, xv, yv)
ans =
logical
 1

Which is completely fine. However, if I have an array which contains x-y coordinates, such as:

K>> xy = [1.5 1.5]
xy =
    1.5000    1.5000

How can I use xy as an input instead of using x and y separately? I do not want to extract x and y manually like:

K>> x = xy(1), y = xy(2)

I want something like:

K>> inpolygon(xy, x, y)
Not enough input arguments.
Error in inpolygon (line 64)
if ~isvector(xv) || ~isvector(yv)

but there is error. Any ideas?

Answer 1

[KSSV]

function out = myinpolygon(xy,x,y) ;
out = inpolygon(xy(:,1),xy(:,2),x,y) ;
end

:)

[Xiaohan Du]

I mentioned in the question that manually separate the inputs as xy(:, 1) and xy(:, 2) is not suitable for my problem.

[KSSV]

Why not suitable?

[Xiaohan Du]

Well, you might be able to do this for this function, but for functions with multiple input, it wouldn't be convenient to manually separate in a way of

aFunction(xy(:, 1), xy(:, 2), xy(:,3), ......)

It's better to be able to do something about xy, such that the function becomes:

aFunction(xy)

Similar to function output, if knowing how many outputs there are, we can always put them into one cell, see: https://www.mathworks.com/matlabcentral/answers/366057-how-to-combine-multiple-output-from-a-function-into-1

[Stephen23]

@Xiaohan Du: In much the same way you can put the input arguments into one cell array, then convert this to a comma-separated list when supplying them to the function. I would not recommend doing this as a general way of calling function though, as it obfuscated the code and makes debugging harder.

[Xiaohan Du]

I see, we can do this:

K>> inpt = {1 2}
inpt =
  1×2 cell array
    [1]    [2]
K>> inpolygon(inpt{:}, xv, yv)
ans =
  logical
   1

such that only 1 input is needed (of course there are still 2 elements in this input).

[Xiaohan Du]

Thank you Stephen!