I keep getting this error in my code

Code:

y = 0.2;
t = 0;
h = 0.01; 
tn = 0.2;
kfv = [30 20 40];
for Kidx = 1 : length(kfv)
    kf = kfv(Kidx);
    %we assume that all the t values are the same
    [t, y(:,Kidx)] = Euler(t, y, h, tn, kf);
end
for Kidx = 1 : length(kfv)
   kf = kfv(Kidx);
   fprintf('The concentration of H2O after %g seconds (kf=%g): %g\n', t(end), kf, y(end, Kidx));
 end
function [t, y] = Euler(t0, y0, h, tn, kf)
    t = (t0:h:tn)';
    y = zeros(size(t));
    y(1) = y0;
    for i = 1:1:length(t)-1
        y(i+1) = y(i) + h*f(y(i), t(i), kf);
    end
end

function dydt = f(y, t, kf)
    c = 0.2;
    b = 0.4;
    a = 0.5;
    dydt = kf*b*a;
end

>> TakeHomeQ1

Assignment has more non-singleton rhs dimensions than non-singleton

subscripts

Error in TakeHomeQ1 (line 9)

[t, y(:,Kidx)] = Euler(t, y, h, tn, kf);

Thanks!

[Walter Roberson]

You have a conflict between y = 0.2 (a scalar), passing y (all of it) into Euler where it gets stored into the scalar location y(1), and receiving the output of Euler (which is length(t)) into y(:,Kidx)