Not a valid target for an assignment

I am trying to do a cross sectional regression and i get the error The expression to the left of the equals sign is not a valid target for an assignment. What should i do?

>> %whole sample CAPM
returns=xlsread('Stock Returns','B2:AE321');
factors=xlsread('Factors','B2:E321');
T=min(size(factors,1),size(returns,1));
beta=ones(30,2);
%Step 1:Time-series regression]
for i=1:30
alpha=[ones(T,1) factors(:,1)];
Y=returns(:,i)-factors(:,4);
coefficients(i,:)=(alpha\Y);
end
%Step 2:Cross-sectional regression
Market_Premium=ones(T,2);
for n=1:T
alpha01=[ones(30,1) coefficients(:,2)
Y=(returns(n,:)-factors(t,4))';
Y=(returns(n,:)-factors(t,4))';
↑
Error: The expression to the left of the equals sign is not a valid target for an assignment.

Answer 1

[dpb]

...
alpha01=[ones(30,1) coefficients(:,2)
Y=(returns(n,:)-factors(t,4))';

The opening [ of the first line isn't terminated so the next line is interpreted as if you'd typed in

alpha01=[ones(30,1) coefficients(:,2) Y=(returns(n,:)-factors(t,4))';

Fix the typo; the editor should have flagged a line there I'd think...

alpha01=[ones(30,1) coefficients(:,2)];

[Loukas Politikos]

thank you very much!