how can i program a matfunction block?

I have 3 batteries with me. I want to turn on the switch of the battery corresponding to the highest state of charge I had done following mathfunction. but it shows some errors

function [s1,s2,s3] = fcn(soc1,soc2,soc3)

y = max([soc1,soc2,soc3]);

if y==soc1

   s1=1;

   s2=0;

   s3=0;

elseif y==soc2

   s2=1;

   s1=0;

   s3=0;

elseif y==soc3

s3=1;

s1=0;

s2=0;

end

end

Answer 1

[Walter Roberson]

[y, idx] = max([soc1, soc2, soc3]);
s1 = 0; s2 = 0; s3 = 0;
if idx == 1; s1 = 1; end
if idx == 2; s2 = 1; end
if idx == 3; s3 = 1; end