Passing array as input to a function

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Hung Yu 2023-8-23

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评论： Dyuman Joshi 2023-8-23

Hi, im trying to pass the following arrays into the self created function DrawRegularPolygon but Matlab is prompting me matrix dimension errors. Can someone help

n = [3,4] ;

D = [2,1] ;

a = [0,0] ;

[xseries, yseries] = DrawRegularPolygon ( n , D , a) ;

function [xseries, yseries] = DrawRegularPolygon ( nosides , Diameter , alpha )

ThetaSeries = ( (0 + alpha).*pi ) : ( 2*pi./nosides ) : ( (2 + alpha).*pi ) ;

xseries = (Diameter./2) .* cos(ThetaSeries) ;

yseries = (Diameter./2) .* sin(ThetaSeries) ;

end

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Stephen23 2023-8-23

在 MATLAB Online 中打开

The outputs are different sizes. You could easily use ARRAYFUN:

n = [3,4] ;
D = [2,1] ;
a = [0,0] ;
[xseries, yseries] = arrayfun(@DrawRegularPolygon, n , D , a, 'uni',false)
xseries = 1×2 cell array
    {[1 -0.5000 -0.5000 1]}    {[0.5000 3.0616e-17 -0.5000 -9.1849e-17 0.5000]}
yseries = 1×2 cell array
    {[0 0.8660 -0.8660 -2.4493e-16]}    {[0 0.5000 6.1232e-17 -0.5000 -1.2246e-16]}
function [xseries, yseries] = DrawRegularPolygon ( nosides , Diameter , alpha ) 
ThetaSeries = ( (0 + alpha).*pi ) : ( 2*pi./nosides ) : ( (2 + alpha).*pi );
xseries = (Diameter./2) .* cos(ThetaSeries);
yseries = (Diameter./2) .* sin(ThetaSeries);
end

Dyuman Joshi 2023-8-23

I did consider using arrayfun, but it seems my bias against using it has grown quite a bit.

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Answer 1

Dyuman Joshi 2023-8-23

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https://ww2.mathworks.cn/matlabcentral/answers/2011647-passing-array-as-input-to-a-function#answer_1291772

编辑：Dyuman Joshi 2023-8-23

在 MATLAB Online 中打开

If you perform colon operations with vectors to create regularly-spaced vectors, it will only take the 1st element of each vector in consideration.

From the documentation of colon, : - "If you specify nonscalar arrays, then MATLAB interprets j:i:k as j(1):i(1):k(1)."

%Example
[1 2]:[0.5 0.75]:[3 4]
ans = 1×5
    1.0000    1.5000    2.0000    2.5000    3.0000

You can use a for loop to make regularly-spaced vectors corresponding to each element of inputs, and since number of elements of the generated vector will vary, use a cell array to store them -

n = [3,4] ;
D = [2,1] ;
a = [0,0] ;
C = DrawRegularPolygon ( n , D , a)
C = 2×2 cell array
    {[         1 -0.5000 -0.5000 1]}    {[0.5000 3.0616e-17 -0.5000 -9.1849e-17 0.5000]}
    {[0 0.8660 -0.8660 -2.4493e-16]}    {[     0 0.5000 6.1232e-17 -0.5000 -1.2246e-16]}

function C = DrawRegularPolygon ( nosides , Diameter , alpha ) 
n = numel(nosides);
%2 row cell array - 1st row for xseries, 2nd row for yseries
C = cell(2,n);
%Assuming all the input variables have same number of elements
for k=1:numel(nosides)
        ThetaSeries = ( (0 + alpha(k)).*pi ) : ( 2*pi./nosides(k) ) : ( (2 + alpha(k)).*pi );
        xseries = (Diameter(k)./2) .* cos(ThetaSeries);
        yseries = (Diameter(k)./2) .* sin(ThetaSeries);
        C{1,k} = xseries;
        C{2,k} = yseries;
end
end

P.S - You can use a check in the code as well to see if the inputs have similar dimensions or not.

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