Index in position 1 exceeds array bounds (must not exceed 61)

When I run my code I get the error Index in position 1 exceeds array bounds (must not exceed 61)

Error in neph_calibration_correction (line 9)

p=polyfit([nephzero(i,2) nephspan(i,2)],[0 11.15],1); %

What am I getting wrong here? I have gone through previous solutions but seems not working.

%% calculate neph slopes

load('neph_zero_span.mat');% nephzero nephspan

nephspan=nephspan([2:4 6:end],:);
spancoefs=zeros(length(nephspan),4).*nan;
for i=1:length(nephspan)
    spancoefs(i,1)=nephspan(i,1);
    p=polyfit([nephzero(i,2) nephspan(i,2)],[0 11.15],1); % red
    spancoefs(i,2)=p(1);
    p=polyfit([nephzero(i,3) nephspan(i,3)],[0 23.86],1); % green
    spancoefs(i,3)=p(1);
    p=polyfit([nephzero(i,4) nephspan(i,4)],[0 44.21],1); % blue
    spancoefs(i,4)=p(1);
end

Answer 1

[KSSV]

This error occurs, when you try to extract more number of elements then present in the array.

A = rand(10,1) ; 
A(1)   % no error

ans = 0.4508

A(7)   % no error

ans = 0.7545

A(11)   % error as there is no 11th element

Index exceeds the number of array elements. Index must not exceed 10.

Check the dimensions of your variables.