working 0 padded interpolation

interpolate.m

function [y, indexy] = myinterpolate(x, N, a_x, b_x)
    a=a_x;
    b=b_x;
    
    x_axis=a:b;
    x_axis_exp=a:length(x_axis)*N;
    x_axis_norm=1:length(x_axis_exp);
    
    y=[];
    indexy=[];
    
    for(i=x_axis_norm)
        k=x_axis_exp(i);
        if(mod(k, N)==0) % sample
            x_val=x(k/N);
            y=[y x_val];
        else % interpolate
            y=[y 0];
        end
        
        indexy=[indexy i];
    end
end