How to call a function and show output of an image

I am trying to learn Hough transform for circle. How can I read an image and use the written function (call the function) to finally display the output? Here is the code

%Hough Transform for Circles

function acc = houghcircle1(inputimage)

%image size

[rows,columns]=size(inputimage);

%accumulator

acc=zeros(rows,columns);

%image

for x=1:columns

for y=1:rows

if(inputimage(y,x)==0)

for ang=0:360

t=(ang*pi)/180;

x0=round(x-a*cos(t));

y0=round(y-r*sin(t));

if(x00 && y00)

acc(y0,x0)=acc(y0,x0)+1;

end

end

end

end

end

end

I tried to read an image I have in my directory and call the function but cannot display the output to see if the code work.

I=imread('screw.jpg');

houghcircle1(I)