Problem with Arithmetic mean/Theissen method with matlab

%Currently I am working on the assignment and I have difficulty on making the code work. The problem is that "Index exceeds matrix dimensions." at "indx= index(pos);"

%Here it my code

%The shape of a drainage basin can be approximate by a polygon whose

%vertices are located at the following coordinates: (5,5), (-5,5), (-5,-5),

%(0,-10), (5,-5)

%Step 1: Catchment Area Coordinates

X = input('X=');

Y = input('Y=');

plot(X,Y,'r','Linewidth',3)

%Step 2: set up gage data

x=[ 7 3 -2 -10 -3 -7 2 2 0]';

y=[ 4 4 5 1 -3 -7 -3 -10 0]';

gages = [x ...

    y];

hold on

scatter(x,y,'b','Marker','*')

text([7; 3; -2; -10; -3; -7; 2; 2; 0],[4; 4; 5; 1; -3; -7; -3; -10; 0],['1';'2';'3';'4';'5';'6';'7';'8';'9'],...

    'HorizontalAlignment','right',...

    'FontSize',12,...

    'FontName','Impact');

voronoi(x(:),y(:))

%3. Calculation of Grid Points

m = input('m = ');

n = input('n = ');

for a=1:m

    for b=1:n

        gx(a,b)=b;

        gy(b,a)=b;

        scatter(a,b,...

            'r','Marker','.')

    end

end

p = cat(2,gx,gy);

%4. grid points

grdpts = (m*n);

r = reshape(p,grdpts,2);

index = 1:grdpts;

for d1 = 1:9

    for d2 = 1:grdpts

        distn = pdist2(gages,r);

    end

    [~, pos] = min(distn);

    indx= index(pos);

end

%5. Nearest Gage to each grid point

numb = zeros(grdpts,1);

for g=1:9

    numb = find(indx==g);

    wt(g,1)= length(numb);

end

numb;

wt;

%6. (a) the arithmetic mean method

aritm_avg_rainfall = mean(rainfall);

%6. (b) The theissen method

theisswts = wt./grdpts;rainfall = input('rainfall =');

Currently