Help doing array to display values on map

Hi I am trying to do an array that will calculate the mean value of the high composite minus the low composite divided by two. After that I am trying to do a t-test of each observation to be able to display it in a map. I started my array like this but matlab is giving me multiple error messages. My dataset is x=141,y=71 and t=38. I have to make this array work for the 38 years. the average of my high composite is 1.69 and the low -1.29 .Any help will be appreciated.

 rain(141,71,38);
    for j1=71
        for i1=141
            zm1=(i,j)=precip(i,j,1;);
        end
    end